Let k = curvature.

Find k given r (t) = t i + t^2 j + (1/2)t^2 k

I found ||T'(t)|| to be (5t + 3)/(5t^2 + 1)^(3/2).

Is this correct?

I found ||r'(t)|| to be sqrt {5t^2 + 1}. Is this correct?

I must find k = ||T'(t)||/||r'(t)||.

The answer is (sqrt {5})/(1 + 5t^2)^(3/2).

Can someone set up the correct fraction to find k?