In Fig.10.15, AOB is the diameter of the circle and C, D, and E are any three points on the semi-circle. Find the value of ACD +
BED.
Join AE
ACDE is a cyclic quadrilateral and the sum of opposite angles in a cyclic quadrilateral is 180°
ACD +
AED = 180° … (i)
Now, we know that the angle in a semi-circle is 90°
So, AEB = 90° … (ii)
By adding equation (i) & (ii), we get.
ACD +
AED +
AEB = 180° + 90°
ACD +
BED = 270°
Hence the value of ACD +
BED is 270°