# Real part of sin^-1 z

Hello, I am to evaluate the real part of $sin^-^1 z = 0.5 (\sqrt{ x^2 +y^2 +2x+1} - \sqrt {x^2 +y^2 -2x+1}$
can someone demonstrate how the identity $sin^-^1 z$ = $\frac{1}{i} ln [ i (z) + \sqrt {1- z^2} ]$
$sin^-^1 z$ = $\frac{1}{i} ln [ i (x+iy) + \sqrt {1- (x+iy)^2} ]$