CBSE Class 9 Answered
ΔABC and ΔADC are right triangles with AC as common hypotenuse.
Two triangles together make a quadrilateral ABCD
In quadrilateral ABCD,
ABC + ADC = 90° + 90° = 180°
Now, sum of opposite angles of a quadrilateral is 180°. (∵ by thm.)
∴ ABCD is a cyclic quadrilateral.
Then, CAD = CBD (∵ angles in the same segment of a circle are equal)