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reduce_trig for matrices

asked 2010-12-29 05:24:53 -0500

mhfrey gravatar image

updated 2011-04-28 11:07:58 -0500

Kelvin Li gravatar image

I am trying to reduce the trig functions of the following symbolic matrix:

[  sin(1/2*B)*cos(1/2*B)  I*sin(1/2*B)^2 - 1/2*I]
[-I*sin(1/2*B)^2 + 1/2*I  -sin(1/2*B)*cos(1/2*B)]

I expect:

[1/2*sin(B), -1/2*I*cos(B)]
[1/2*I*cos(B), -1/2*sin(B)]

But get: Traceback (click to the left of this block for traceback) ... AttributeError: 'sage.matrix.matrix_symbolic_dense.Matrix_symbolic_dense' object has no attribute 'reduce_trig'

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>
  File "", line 10, in <module>
    exec compile(u'open("","w").write("# -*- coding: utf-8 -*-\\n" + _support_.preparse_worksheet_cell(base64.b64decode("KFJ4KEIpKkl5KlJ4KC1CKSkucmVkdWNlX3RyaWcoKQ=="),globals())+"\\n"); execfile(os.path.abspath(""))
  File "", line 1, in <module>

  File "/tmp/tmpTc7DZX/", line 2, in <module>
    exec compile(u'(Rx(B)*Iy*Rx(-B)).reduce_trig()
  File "", line 1, in <module>

  File "element.pyx", line 306, in sage.structure.element.Element.__getattr__ (sage/structure/element.c:2666)
  File "parent.pyx", line 272, in sage.structure.parent.getattr_from_other_class (sage/structure/parent.c:2840)

What am I doing wrong?

Thank you for your help.

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you can use the "code" button (little picture of 0's and 1's) to format code (such as the traceback lines) correctly

niles gravatar imageniles ( 2010-12-29 05:29:06 -0500 )edit
kcrisman gravatar imagekcrisman ( 2011-01-03 15:02:11 -0500 )edit

3 answers

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answered 2010-12-29 05:31:07 -0500

niles gravatar image

You could try using apply_map, as suggested here:

Is there a way to simplify_full and trig_reduce a matrix?

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answered 2011-05-16 09:20:55 -0500

kcrisman gravatar image

As it turns out, we already have it, just not with all possible aliases! I didn't even know this.

sage: m = matrix([[sin(x), cos(x)], [sin(x), cos(x)]]); m
[sin(x) cos(x)]
[sin(x) cos(x)]
sage: o = m*m.transpose()
sage: o.simplify_trig()
[1 1]
[1 1]

But the ticket referenced in the comment above should make all of them available.

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answered 2010-12-29 06:04:16 -0500

mhfrey gravatar image

That works, Thank you for the fix.

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Asked: 2010-12-29 05:24:53 -0500

Seen: 234 times

Last updated: May 16 '11