everything to the right of the square root symbol are supposed to be under the square root symbol; x*x=x2
We are looking for the sin of a triangle whose cos = x = x / 1
So......the hypotenuse = 1 = r
And the sin = sqrt ( r^2 - x^2) / r = sqrt ( 1 - x^2) / 1 = sqrt (1 - x^2 )
