Find the length of the curve. r(t) = 3t, 3 cos t, 3 sin t , −4 ≤ t ≤ 4

we are given

we can compare it with

we get

now, we can use length formula

now, we can find x' , y' and z'

now, we can plug values

and we get

now, we can simplify it

we get

............Answer