Given a square ABCD of sides 10 cm, and using the corners as
centres, construct four quadrants with radius 10 cm each inside the
square. The four arcs intersect at P, Q, R and S. Find the area
enclosed by PQRS.

Two Circles

Stage: 4 Challenge Level:

Draw two circles, each of radius $1$ unit, so that each circle
goes through the centre of the other one. What is the area of the
overlap?