Find the Fourier coefficients of the piecewise continuousfunction

f(t) = {0 if t <= (less than or equal to) 0 or 1 if t > 0.}

I get why Ck is equal to 0. But why is Bk = 2/(k(pi)) when k is odd. And why is A0 = 1/(root(2)). Thanks for any help.

(sorry its written in straight text)