Draw a circle with radius 4cm and center P. Draw another circle of same radius and with center at Q such that it intersects the previous circle. Join PQ. Now join the points of intersection and name this line segment as AB. Mark the point of intersection of AB and PQ as O.
∠AOP =
If you draw step by step as given in the question, you would get:
We can clearly see that ∠AOP = 90∘.