Find Speed of Particle: Position Function r(t)= et(cos(t)i+sin(t)j+7tk)

[julz3216]

Homework Statement

Consider the following position function.
r(t)= et(cos(t)i+sin(t)j+7tk)

Find the speed of a particle with the given position function.

Homework Equations

I know I take the derivative of the function but I can't seem to get speed.
I got v=e^t(cos(t)i+sin(t)j+7(t)k)+ e^t(-sin(t)i+cos(t)j+7k)

The Attempt at a Solution

I just can't find the speed, i think i may be just slightly off. I currently have speed is 7e^t(t+1) which is wrong.

 

[rootX]

Edit:

You are simply using "k" part, where is your i and j part. They don't cancel out.