Step-by-step explanation:
AC is the radius of the circle. BC has the same length as AC.
A 90 degree angle is formed at A, similarly ay B.
A quadrilateral is then formed.
The sum of angles in a quadrilateral is 360 degrees
We have:
A + B + C + D = 360
90 + 90 + C + D = 360
C + D = 360 - 180
C + D = 180
Hence the proof