y`=2arccos√(1-x^2)*(arccos√(1-x^2))`
arccos√(1-x^2)`=-1/√(1-(1-x^2))*1/(2√(1-x^2)*(-2x)=x/(|x|*√(1-x^2))
y`=2arccos√(1-x^2)*x/(|x|√(1-x^2)
y`=2arccos√(1-x^2)*(arccos√(1-x^2))`
arccos√(1-x^2)`=-1/√(1-(1-x^2))*1/(2√(1-x^2)*(-2x)=x/(|x|*√(1-x^2))
y`=2arccos√(1-x^2)*x/(|x|√(1-x^2)