Find the critical numbers of the function. I have two(?).

1. x square root(4-x) (This is what I did)

square root(4-x)(1)+(x) ((4-x))/((2 square root(4-x))

square root(4-x)+((1x))/((2 square root 4-x))

I think I differentiated for it but how would I factor to find the critical numbers?

2. sin^2(x)+cos(x)

cos^2(x)-sin(x)

Here I have the same issue as my top problem