# 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