If X1,X2 .....Xn are independent N(0,1) random variables, do the following

(1) Find the probability density function of U = X^2

HINT : The density function is F(u)= d/duP[X^2 <= u]

Ok so far i think it is

f(u) = d/du[1- P[x^2 > u]

= -d/duP[x^2 > u]

Is this right??