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evaluate (simplify) trigonometric expression

asked 2018-04-12 12:13:32 -0500

watty_ gravatar image
t = var('t')
R = vector ((3*cos(t), 3*sin(t), 4*t))

dRdt = R.diff(t)
show(dRdt)

ds = dRdt.norm()
show(ds)

when I try to show ds it gives mi a trigonometric expression which is actually is equal to 5. I tried simplify() and trig_simplify but it didn't help...

Any tips are welcome. Thanks in advance

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answered 2018-04-12 14:03:55 -0500

Emmanuel Charpentier gravatar image

updated 2018-04-12 14:55:38 -0500

Well...

sage: R=vector([3*cos(t),3*sin(t),4*t]);R
(3*cos(t), 3*sin(t), 4*t)
sage: with assuming(t,"real"): (R.diff(t).norm()^2).trig_reduce().sqrt()
5

or even :

sage: with assuming(t,"real"): R.diff(t).norm().trig_reduce()
5

Is that acceptable to you ?

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Asked: 2018-04-12 12:13:32 -0500

Seen: 20 times

Last updated: Apr 12