#821 csc & trigexpand

[Barton Willis]

I think trigexpandtimes with csc is buggy:

(%i59) csc(3*x),trigexpand;
(%o59) (csc(x)^3*sec(x)^3)/(3*csc(x)*sec(x)^2-csc(x)
^3)
(%i60) %-csc(3*x);
(%o60) (csc(x)^3*sec(x)^3)/(3*csc(x)*sec(x)^2-csc(x)
^3)-csc(3*x)
(%i61) subst(x=0.3,%);
(%o61) -2.8853320239249447 <-- should be zero.

Barton

[Raymond Toy]

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user_id=28849

In csc\Sec-times, the last lines says

\(sin\Cos-times l m n f1 f2 flag\)\)\)

If we swap f1 and f2 like so:

\(sin\Cos-times l m n f2 f1 flag\)\)\)

With this change:

(%i35) csc(3*x),trigexpand;

(%o35) csc(x)^3*sec(x)^3/(3*csc(x)^2*sec(x)-sec(x)^3)
(%i36) ev(%-csc(3*x),x=0.3);

(%o36) -6.661338147750939e-16

This looks better.

[Raymond Toy]

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user_id=28849

Suggested fix applied.