Suppose h = sin(x)
then
color(white)("XXXX")cos(x) = sqrt(1-h^2)
sin(x)*cos(x)= sqrt(2)/4 is equivalent to
color(white)("XXXX")h(sqrt(1-h^2))= sqrt(2)/4
color(white)("XXXX")sqrt(1-h^2) = sqrt(2)/(4h)
color(white)("XXXX")1-h^2 = 2/(16h^2)
color(white)("XXXX")16h^4-16h^2+2=0
Let k=h^2
color(white)("XXXX")8k^2-8k+1=0
color(white)("XXXX")k= (8+-sqrt(64-32))/16
color(white)("XXXX")color(white)("XXXX")=(2+sqrt(2))/4 or (2-sqrt(2))/4
color(white)("XXXX")h = sqrt((2+sqrt(2))/4) or sqrt((2-sqrt(2)/4)
(using my handy calculator)
color(white)("XXXX")h = 0.92388 or 0.382683
x = arcsin(h)
(and again with my calculator)
color(white)("XXXX")x=(3pi)/8 or pi/8
Given that x came out as such pretty values, I expect there is a better (prettier) way to do this.