Hi all,

I need to find the arc length parametrisation of alpha = ( (1-t^2)/(1+t^2) , (2t)/(1+t^2) )

So first of all I differentiated to find alpha' = ( (-4t) / (1+t^2)^2 , (2-2t^2) / (1+t^2)^2 )

and then tried sqrt(x^2 + y^2) but didn't get anything near what the answer is supposed to be ( |alpha'| = 2 / 1 + t^2 )

Please help!!

Many thanks