Question

The angle subtended by the common chord of the circle x^2+y^2-4x-4y=0 and x^2+y^2=16 at the origin is ?

Answer 1

the two circles intersect at:
(0,4) and (4,0)

the angle subtended by the line joining these two points = ?

Answer 2

angle between the position vectors = \(\Large{\pi\over2}\)