Q 11. ABC and ADC are two right triangles with common hypotenuse AC. Prove that $\angle C A D=\angle C B D$..
Given: ABC and ADC are two right triangles with common hypotenuse AC.
To prove : $\angle C A D=\angle C B D$
Proof :
Triangle ABC and ADC are on a common base BC and $\angle \mathrm{BAC}=\angle \mathrm{BDC}$.
Thus, points A, B, C, and D lie in the same circle.
(If a line segment joining two points subtends equal angles at two other points lying on the same side of the line containing the line segment, four points lie on the circle.)
$\angle C A D=\angle C B D$ (Angles in the same segment are equal)