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### evaluate (simplify) trigonometric expression

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