Question

R(t)=e^t sin(t)i+ e^t cos(t) + √(2e^t)k

a) Find the arc length function for the curve measured from the point in the direction of increasing t and then reparametrize the curve with respect to arc length starting from P.
b) Find the point 4 units along the curve (in the direction of increasing t) from P.

I got
r'(t)=e^t (cos(t)+sin(t))I+e^t (cos(t)-sin(t))+ e^t /√(2e^t)
For lr'(t)l= √(5/2) Is this right? And don't know what to do next.