bug#25652: 26.0.50; calc says that cos(1 degree) is 0.54

bug#25652: 26.0.50; calc says that cos(1 degree) is 0.54

[Torsten Bronger]

In Emacs calc usind degree mode, cos(1) results in 0.540302305868
instead of 0.999847695156.


In GNU Emacs 26.0.50.3 (x86_64-pc-linux-gnu)
 of 2017-02-08 built on wilson
Repository revision: c8ee570a8be7afaae3ea318b9d7dbffb62a7bbd0
Windowing system distributor 'The X.Org Foundation', version 11.0.11804000
System Description:	Ubuntu 16.04.1 LTS

Recent messages:
Mark set [2 times]
Saving file /home/bronger/src/totorio/certbot/certbot_master.py...
Wrote /home/bronger/src/totorio/certbot/certbot_master.py
C-c * is undefined
C-x *  (Type ? for a list of Calc options)
Loading /home/bronger/.calc.el (source)...done
Welcome to the GNU Emacs Calculator!  Press ‘?’ or ‘h’ for help, ‘q’ to quit
Working... [2 times]
Angles measured in radians
Working...

Configured using:
 'configure --prefix=/usr/local/ --mandir=/usr/local/share/man/
 --infodir=/usr/local/share/info/ --with-x-toolkit=no --without-makeinfo
 --with-xpm --with-jpeg --with-tiff --with-gif --with-png --with-x'

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND DBUS GSETTINGS NOTIFY GNUTLS LIBXML2
FREETYPE XFT ZLIB X11

Important settings:
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  value of $LANG: de_DE.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Calculator

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-- 
Torsten Bronger

bug#25652: 26.0.50; calc says that cos(1 degree) is 0.54

[Eli Zaretskii]

> From: Torsten Bronger <bronger@physik.rwth-aachen.de>
> Date: Wed, 8 Feb 2017 08:37:57 +0100
> 
> 
> In Emacs calc usind degree mode, cos(1) results in 0.540302305868
> instead of 0.999847695156.

Are you sure you were in degree mode?

bug#25652: 26.0.50; calc says that cos(1 degree) is 0.54

[Torsten Bronger]

Hallöchen!

Eli Zaretskii writes:

>> From: Torsten Bronger <bronger@physik.rwth-aachen.de>
>> Date: Wed, 8 Feb 2017 08:37:57 +0100
>> 
>> 
>> In Emacs calc usind degree mode, cos(1) results in 0.540302305868
>> instead of 0.999847695156.
>
> Are you sure you were in degree mode?

Absolutely.  And funny enough, cos(90) resulted in zero(!).  For the
whole time, Deg was in the modeline, and I didn't switch anything.
Also with "emacs -q".  The sequence "m d 90 C 1 C m r 90 C 1 C"
yields:

0
0.540302305868
-0.448073616129
0.540302305868

Tschö,
Torsten.

-- 
Torsten Bronger

bug#25652: 26.0.50; calc says that cos(1 degree) is 0.54

[Óscar Fuentes]

Torsten Bronger <bronger@physik.rwth-aachen.de> writes:

> In Emacs calc usind degree mode, cos(1) results in 0.540302305868
> instead of 0.999847695156.
>
>
> In GNU Emacs 26.0.50.3 (x86_64-pc-linux-gnu)
>  of 2017-02-08 built on wilson

After pulling and building *right* *now* M-x version says

GNU Emacs 26.0.50.1 (x86_64-pc-linux-gnu, X toolkit) of 2017-02-08

Why the OP version is 26.0.50.3 ?

> Repository revision: c8ee570a8be7afaae3ea318b9d7dbffb62a7bbd0

This revision exists and is one behind `master' on my checkout.

BTW, I can't reproduce the problem following the recipe described by the
OP on his other message.

bug#25652: 26.0.50; calc says that cos(1 degree) is 0.54

[Noam Postavsky]

On Wed, Feb 8, 2017 at 2:31 PM, Óscar Fuentes <ofv@wanadoo.es> wrote:
> Torsten Bronger <bronger@physik.rwth-aachen.de> writes:
>
>> In Emacs calc usind degree mode, cos(1) results in 0.540302305868
>> instead of 0.999847695156.
>>
>>
>> In GNU Emacs 26.0.50.3 (x86_64-pc-linux-gnu)
>>  of 2017-02-08 built on wilson
>
> After pulling and building *right* *now* M-x version says
>
> GNU Emacs 26.0.50.1 (x86_64-pc-linux-gnu, X toolkit) of 2017-02-08
>
> Why the OP version is 26.0.50.3 ?

The last number is the build number, and just counts the number of
times you rebuilt Emacs locally, see #25590.

>
>> Repository revision: c8ee570a8be7afaae3ea318b9d7dbffb62a7bbd0
>
> This revision exists and is one behind `master' on my checkout.
>
> BTW, I can't reproduce the problem following the recipe described by the
> OP on his other message.
>

I can't reproduce it either, cos(1) gives the expected 0.999847695156
in degree mode.

4:  0
3:  0.999847695156
2:  -0.448073616129
1:  0.540302305868

bug#25652: 26.0.50; calc says that cos(1 degree) is 0.54

[Torsten Bronger]

Hallöchen!

Okay, I have one computer on which I can reproduce this bug
reliably, with "emacs -q" and a fresh checkout.  And another
computer on which the bug does not occur.  The most significant
difference is Ubuntu 16.04 vs Ubuntu 16.10.

If I just wanted to gt rid of the problem, I would remove my git
repo and make a fresh clone.  However, maybe you are interested in
me doing further tests before?  Or should I just try to get rid of
the problem?

FWIW, at
https://bob.ipv.kfa-juelich.de/bronger/emacs_bug_25652.tar.gz you
can download my copy Emacs' source code (700MB, 10 MB/sec link).  It
also contains the script I use to update my local Emacs
installation.

Tschö,
Torsten.

-- 
Torsten Bronger

bug#25652: 26.0.50; calc says that cos(1 degree) is 0.54

[npostavs]

Torsten Bronger <bronger@physik.rwth-aachen.de> writes:

> Hallöchen!
>
> Okay, I have one computer on which I can reproduce this bug
> reliably, with "emacs -q" and a fresh checkout.  And another
> computer on which the bug does not occur.  The most significant
> difference is Ubuntu 16.04 vs Ubuntu 16.10.

Does it happen also with "emacs -Q"?  I think the uppercase version
disables a few more customizations.

Anyway, I suggest instrumenting calc-cos and stepping with edebug until
something weird happens.

PS: you have "Mail-Followup-To: bug-gnu-emacs@gnu.org" in your headers
which is wrong, because followups should go to 25652@debbugs.gnu.org, so
I ignored that and the "Mail-Copies-To: never" header.

bug#25652: 26.0.50; calc says that cos(1 degree) is 0.54

[Glenn Morris]

npostavs@users.sourceforge.net wrote:

> PS: you have "Mail-Followup-To: bug-gnu-emacs@gnu.org" in your headers
> which is wrong, because followups should go to 25652@debbugs.gnu.org, so
> I ignored that and the "Mail-Copies-To: never" header.

FWIW it's not wrong, in that bug-gnu-emacs@gnu.org and
25652@debbugs.gnu.org are equivalent, so long as one does not mess with
the subject or references headers. But the latter is definitely better,
and personally I would discourage use of MFT in general, since it often
leads to people getting dropped from the reply chain.

Anyway, what about this:

  Loading /home/bronger/.calc.el (source)...done

I don't think this respects -Q?

bug#25652: 26.0.50; calc says that cos(1 degree) is 0.54

[Torsten Bronger]

Hallöchen!

Glenn Morris writes:

> npostavs@users.sourceforge.net wrote:
>
>> PS: you have "Mail-Followup-To: bug-gnu-emacs@gnu.org" in your
>> headers which is wrong, because followups should go to
>> 25652@debbugs.gnu.org, so I ignored that and the "Mail-Copies-To:
>> never" header.
>
> FWIW it's not wrong, in that bug-gnu-emacs@gnu.org and
> 25652@debbugs.gnu.org are equivalent, so long as one does not mess
> with the subject or references headers. But the latter is
> definitely better, and personally I would discourage use of MFT in
> general, since it often leads to people getting dropped from the
> reply chain.

I use gmane.org for using this mailing list like a newsgroup.  Sorry
if this causes trouble.  If it is too much, I switch to ordinary
mail, however, gmane really *is* convenient.

> Anyway, what about this:
>
>   Loading /home/bronger/.calc.el (source)...done

This hint was very helpful!  I totally forgot about my calc
customization.  (Well, it is slightly inconsistent that it is read
by emacs -Q but anyway.)  The error-provoking part in it is:

(setq calc-simplify-mode 'units)

You can toggle this in calc mode with "m U".  So "m d m U 1 C m U 1
C" should exhibit the problem.  Note that you have "Deg" active the
whole time.  The manual says about unit simplification:

    The functions sin, cos, and tan with arguments that have angular
    units like rad or arcmin are simplified by converting to base
    units (radians), then evaluating with the angular mode
    temporarily set to radians.

While this explains part of my observations, I find it very
confusing that "1 C" may yield 0.54 while in "Deg" mode.

And, "90 C" always yielding zero is definitely inconsistent.
"89.999 C" yields -0.447984214223 while in unit simplification mode,
so the cosine is not continuous anymore.

Tschö,
Torsten.

-- 
Torsten Bronger

bug#25652: 26.0.50; calc says that cos(1 degree) is 0.54

[Torsten Bronger]

Hallöchen!

Torsten Bronger writes:

> [...]
>
> You can toggle this in calc mode with "m U".  So "m d m U 1 C m U
> 1 C" should exhibit the problem.  Note that you have "Deg" active
> the whole time.

Unfortunately, my second machine still does not exhibit this
problem, as doesn't probably yours.  So I have to dig deeper.

This is really odd, since both machines are so similar.  (They even
mount the same $HOME.)

Tschö,
Torsten.

-- 
Torsten Bronger

bug#25652: 26.0.50; calc says that cos(1 degree) is 0.54

[Torsten Bronger]

Hallöchen!

Torsten Bronger writes:

> [...]
>
> You can toggle this in calc mode with "m U".  So "m d m U 1 C m U
> 1 C" should exhibit the problem.  Note that you have "Deg" active
> the whole time.  [...]

After havin updated to current git master, I can now reproduce this
on both of my machine.  Can you confirm?

> [...]
>
> And, "90 C" always yielding zero is definitely inconsistent.
> "89.999 C" yields -0.447984214223 while in unit simplification mode,
> so the cosine is not continuous anymore.

As I can reproduce this.

Tschö,
Torsten.

-- 
Torsten Bronger

bug#25652: 26.0.50; calc says that cos(1 degree) is 0.54

[npostavs]

tags 25652 confirmed
retitle 25652 26.0.50; [calc] In Units Simplication + Degree mode cos(1 deg) != cos(1)
quit

Torsten Bronger <bronger@physik.rwth-aachen.de> writes:
>> You can toggle this in calc mode with "m U".  So "m d m U 1 C m U
>> 1 C" should exhibit the problem.  Note that you have "Deg" active
>> the whole time.  [...]
>
> After havin updated to current git master, I can now reproduce this
> on both of my machine.  Can you confirm?

Yes, this happens in units simplication mode.  Note that 'cos(1 deg) RET
does give 0.999.  It seems to be because of the fix for #23889 [1:
713e922243].  Tino, any ideas?

1: 2016-07-12 00:38:14 +0900 713e922243fb60d850f7b0ff83f3e2a3682f1832
  Ignore angle mode while simplifying units

bug#25652: 26.0.50; calc says that cos(1 degree) is 0.54

[Tino Calancha]

[Forwading to the bug thread: Sorry if you receive this message twice]

npostavs@users.sourceforge.net writes:

> tags 25652 confirmed
> retitle 25652 26.0.50; [calc] In Units Simplication + Degree mode cos(1 deg) != cos(1)
> quit
>
> Torsten Bronger <bronger@physik.rwth-aachen.de> writes:
>>> You can toggle this in calc mode with "m U".  So "m d m U 1 C m U
>>> 1 C" should exhibit the problem.  Note that you have "Deg" active
>>> the whole time.  [...]
>>
>> After havin updated to current git master, I can now reproduce this
>> on both of my machine.  Can you confirm?
>
> Yes, this happens in units simplication mode.  Note that 'cos(1 deg) RET
> does give 0.999.  It seems to be because of the fix for #23889 [1:
> 713e922243].  Tino, any ideas?
>
> 1: 2016-07-12 00:38:14 +0900 713e922243fb60d850f7b0ff83f3e2a3682f1832
>   Ignore angle mode while simplifying units
Yes, my commit produced this bug.  We must revert it.  Sorry for that.
That commit was to fix Bug#23889.  It would be nice if we can fix Bug#23889 in
a new way.
In that bug the problem was that, if the user inputs a symbolic expression containning
an angle unit, then this unit is overriden by calc-angle-mode while simplifying such
expression.
That should not happen as mentioned in the manual:
(info "(calc) Trigonometric and Hyperbolic Functions")

That is,
M-x calc RET
m d ; Set calc-angle-mode to degrees.
' sin (45 deg) RET
u s ; Must insert the value of:  (sin (* 45 pi (/ 180.0)))
;; But instead, inserts the value of: (sin (* 45 (expt (/ pi 180.0) 2)))
;; i.e., it's applying (/ pi 180) twice.

I have updated the patch:
1) Revert 713e922243

2) Bind calc-angle-mode to 'rad while simplifying an expression whenever such
expression contains an unit angle.  This way, hopefully, the second factor (/ pi 180)
won't be applied.

Opinions, comments...
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
From 1a2592409c0fcfca7826b71248d3d3d234355c13 Mon Sep 17 00:00:00 2001
From: Tino Calancha <tino.calancha@gmail.com>
Date: Sun, 12 Feb 2017 21:14:34 +0900
Subject: [PATCH 1/2] Revert 'Ignore angle mode while simplifying units'

This commit (713e922243) cause regressions (Bug#25652).
---
  lisp/calc/calc-forms.el | 12 +++---------
  lisp/calc/calc-math.el  | 12 ++++--------
  2 files changed, 7 insertions(+), 17 deletions(-)

diff --git a/lisp/calc/calc-forms.el b/lisp/calc/calc-forms.el
index 6aa421ec20..abf76cf07e 100644
--- a/lisp/calc/calc-forms.el
+++ b/lisp/calc/calc-forms.el
@@ -317,9 +317,7 @@ math-to-hms
  	 (list 'calcFunc-hms a))
  	((math-negp a)
  	 (math-neg (math-to-hms (math-neg a) ang)))
-	((eq (or ang
-                 (and (not math-simplifying-units) calc-angle-mode))
-                 'rad)
+	((eq (or ang calc-angle-mode) 'rad)
  	 (math-to-hms (math-div a (math-pi-over-180)) 'deg))
  	((memq (car-safe a) '(cplx polar)) a)
  	(t
@@ -356,16 +354,12 @@ math-from-hms
  	   (if (eq (car-safe a) 'sdev)
  	       (math-make-sdev (math-from-hms (nth 1 a) ang)
  			       (math-from-hms (nth 2 a) ang))
-	     (if (eq (or ang
-                         (and (not math-simplifying-units) calc-angle-mode))
-                     'rad)
+	     (if (eq (or ang calc-angle-mode) 'rad)
  		 (list 'calcFunc-rad a)
  	       (list 'calcFunc-deg a)))))
  	((math-negp a)
  	 (math-neg (math-from-hms (math-neg a) ang)))
-	((eq (or ang
-                 (and (not math-simplifying-units) calc-angle-mode))
-             'rad)
+	((eq (or ang calc-angle-mode) 'rad)
  	 (math-mul (math-from-hms a 'deg) (math-pi-over-180)))
  	(t
  	 (math-add (math-div (math-add (math-div (nth 3 a)
diff --git a/lisp/calc/calc-math.el b/lisp/calc/calc-math.el
index 2590761d53..faa318d45d 100644
--- a/lisp/calc/calc-math.el
+++ b/lisp/calc/calc-math.el
@@ -763,14 +763,12 @@ calcFunc-nroot
  (defun math-to-radians (a)   ; [N N]
    (cond ((eq (car-safe a) 'hms)
  	 (math-from-hms a 'rad))
-	((and (not math-simplifying-units)
-              (memq calc-angle-mode '(deg hms)))
+	((memq calc-angle-mode '(deg hms))
  	 (math-mul a (math-pi-over-180)))
  	(t a)))

  (defun math-from-radians (a)   ; [N N]
-  (cond ((and (not math-simplifying-units)
-              (eq calc-angle-mode 'deg))
+  (cond ((eq calc-angle-mode 'deg)
  	 (if (math-constp a)
  	     (math-div a (math-pi-over-180))
  	   (list 'calcFunc-deg a)))
@@ -781,16 +779,14 @@ math-from-radians
  (defun math-to-radians-2 (a &optional force-symbolic)   ; [N N]
    (cond ((eq (car-safe a) 'hms)
  	 (math-from-hms a 'rad))
-	((and (not math-simplifying-units)
-              (memq calc-angle-mode '(deg hms)))
+	((memq calc-angle-mode '(deg hms))
  	 (if (or calc-symbolic-mode force-symbolic)
  	     (math-div (math-mul a '(var pi var-pi)) 180)
  	   (math-mul a (math-pi-over-180))))
  	(t a)))

  (defun math-from-radians-2 (a &optional force-symbolic)   ; [N N]
-  (cond ((and (not math-simplifying-units)
-              (memq calc-angle-mode '(deg hms)))
+  (cond ((memq calc-angle-mode '(deg hms))
  	 (if (or calc-symbolic-mode force-symbolic)
  	     (math-div (math-mul 180 a) '(var pi var-pi))
  	   (math-div a (math-pi-over-180))))
-- 
2.11.0

From b1b6f62f5baa8023a7b5d45b1d30399c8e8f82a2 Mon Sep 17 00:00:00 2001
From: Tino Calancha <tino.calancha@gmail.com>
Date: Sun, 12 Feb 2017 21:45:47 +0900
Subject: [PATCH 2/2] Prevent from override input angle unit while simplifying

Ignore calc-angle-mode while simplifying if the expression
contains angle units (Bug#23899).
* lisp/calc/calc-alg.el (calc-input-angle-units): New defun.
(math-simplify): If TOP-EXPR contains angle units, then bind
calc-angle-mode to 'rad.
* test/lisp/calc/calc-tests.el (test-calc-23889): New test.
---
  lisp/calc/calc-alg.el        |  9 +++++++++
  test/lisp/calc/calc-tests.el | 46 ++++++++++++++++++++++++++++++++++++++++++++
  2 files changed, 55 insertions(+)

diff --git a/lisp/calc/calc-alg.el b/lisp/calc/calc-alg.el
index 4e63d238c7..9db901a975 100644
--- a/lisp/calc/calc-alg.el
+++ b/lisp/calc/calc-alg.el
@@ -355,10 +355,19 @@ math-hyperbolic-trig-rewrite
  ;; math-simplify-step, which is called by math-simplify.
  (defvar math-top-only)

+(defun calc-input-angle-units (input)
+  (cond ((math-expr-contains input '(var deg var-deg)) 'deg)
+        ((math-expr-contains input '(var rad var-rad)) 'rad)
+        ((math-expr-contains input '(var hms var-hms)) 'hms)
+        (t nil)))
+
  ;; math-normalize-error is declared in calc.el.
  (defvar math-normalize-error)
  (defun math-simplify (top-expr)
    (let ((math-simplifying t)
+        (calc-angle-mode (if (calc-input-angle-units top-expr)
+                             'rad
+                           calc-angle-mode))
  	(math-top-only (consp calc-simplify-mode))
  	(simp-rules (append (and (calc-has-rules 'var-AlgSimpRules)
  				 '((var AlgSimpRules var-AlgSimpRules)))
diff --git a/test/lisp/calc/calc-tests.el b/test/lisp/calc/calc-tests.el
index 8f56d48d01..45b735c3c6 100644
--- a/test/lisp/calc/calc-tests.el
+++ b/test/lisp/calc/calc-tests.el
@@ -86,6 +86,52 @@ calc-tests-simple
  					       (math-read-expr "1m") "cm")
  			    '(* -100 (var cm var-cm)))))

+(ert-deftest test-calc-23889 ()
+  "Test for http://debbugs.gnu.org/23889 and 25652."
+  (dolist (mode '(deg rad))
+    (let ((calc-angle-mode mode))
+      ;; If user inputs angle units, then should ignore `calc-angle-mode'.
+      (should (string= "5253"
+                       (substring
+                        (number-to-string
+                         (nth 1
+                              (math-simplify-units
+                               '(calcFunc-cos (* 45 (var rad var-rad))))))
+                        0 4)))
+      (should (string= "7071"
+                       (substring
+                        (number-to-string
+                         (nth 1
+                              (math-simplify-units
+                               '(calcFunc-cos (* 45 (var deg var-deg))))))
+                        0 4)))
+      (should (string= "8939"
+                       (substring
+                        (number-to-string
+                         (nth 1
+                              (math-simplify-units
+                               '(+ (calcFunc-sin (* 90 (var rad var-rad)))
+                                   (calcFunc-cos (* 90 (var deg var-deg)))))))
+                        0 4)))
+      (should (string= "5519"
+                       (substring
+                        (number-to-string
+                         (nth 1
+                              (math-simplify-units
+                               '(+ (calcFunc-sin (* 90 (var deg var-deg)))
+                                   (calcFunc-cos (* 90 (var rad var-rad)))))))
+                        0 4)))
+      ;; If user doesn't input units, then must use `calc-angle-mode'.
+      (should (string= (if (eq calc-angle-mode 'deg)
+                           "9998"
+                         "5403")
+                       (substring
+                        (number-to-string
+                         (nth 1
+                              (math-simplify-units
+                               '(calcFunc-cos 1))))
+                        0 4))))))
+
  (provide 'calc-tests)
  ;;; calc-tests.el ends here

-- 
2.11.0

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
In GNU Emacs 26.0.50.1 (x86_64-pc-linux-gnu, GTK+ Version 3.22.7)
  of 2017-02-12
Repository revision: 862d6438cfa6c6c035033697751f3d002357b024

bug#25652: 26.0.50; calc says that cos(1 degree) is 0.54

[npostavs]

Tino Calancha <tino.calancha@gmail.com> writes:

> Yes, my commit produced this bug.  We must revert it.  Sorry for that.
> That commit was to fix Bug#23889.  It would be nice if we can fix Bug#23889 in
> a new way.
> In that bug the problem was that, if the user inputs a symbolic expression containning
> an angle unit, then this unit is overriden by calc-angle-mode while simplifying such
> expression.
> That should not happen as mentioned in the manual:
> (info "(calc) Trigonometric and Hyperbolic Functions")
>
> That is,
> M-x calc RET
> m d ; Set calc-angle-mode to degrees.
> ' sin (45 deg) RET
> u s ; Must insert the value of:  (sin (* 45 pi (/ 180.0)))
> ;; But instead, inserts the value of: (sin (* 45 (expt (/ pi 180.0) 2)))
> ;; i.e., it's applying (/ pi 180) twice.
>
> I have updated the patch:
> 1) Revert 713e922243
>
> 2) Bind calc-angle-mode to 'rad while simplifying an expression whenever such
> expression contains an unit angle.  This way, hopefully, the second factor (/ pi 180)
> won't be applied.
>
> Opinions, comments...

I'm not familiar enough with calc to say if this is a good idea or not,
but I guess you may as well push this now so that we can discover if it
has any problems sooner rather than later.

bug#25652: 26.0.50; calc says that cos(1 degree) is 0.54

[Tino Calancha]

npostavs@users.sourceforge.net writes:

> Tino Calancha <tino.calancha@gmail.com> writes:
>
>> Yes, my commit produced this bug.  We must revert it.  Sorry for that.
>> That commit was to fix Bug#23889.  It would be nice if we can fix Bug#23889 in
>> a new way.
>> In that bug the problem was that, if the user inputs a symbolic expression containning
>> an angle unit, then this unit is overriden by calc-angle-mode while simplifying such
>> expression.
>> That should not happen as mentioned in the manual:
>> (info "(calc) Trigonometric and Hyperbolic Functions")
>>
>> That is,
>> M-x calc RET
>> m d ; Set calc-angle-mode to degrees.
>> ' sin (45 deg) RET
>> u s ; Must insert the value of:  (sin (* 45 pi (/ 180.0)))
>> ;; But instead, inserts the value of: (sin (* 45 (expt (/ pi 180.0) 2)))
>> ;; i.e., it's applying (/ pi 180) twice.
>>
>> I have updated the patch:
>> 1) Revert 713e922243
>>
>> 2) Bind calc-angle-mode to 'rad while simplifying an expression whenever such
>> expression contains an unit angle.  This way, hopefully, the second factor (/ pi 180)
>> won't be applied.
>>
>> Opinions, comments...
>
> I'm not familiar enough with calc to say if this is a good idea or not,
> but I guess you may as well push this now so that we can discover if it
> has any problems sooner rather than later.

Thank you.  I've reverted my buggy fix, and pushed a new fix
for Bug#23889 into master:

Revert:
eab1a6307b09180bd775cfb6bf7330eb5367bbe0
Fix:
c48e539226a062d01b8d5534644fae959506a743