Verified answer

y=arc cos(x/2)

we use the rule of arc cos x= - 1/sqrt(1-x^2)

solution:

..................-1

dy/dx=------------------- d/dx 1/2

............√(1-(x/2)^2)

.............-1

=-----------------------

.....2√1-(x^2/4)

............-1

=--------------------- answer//

.......2√(4-x^2)