Question

Why angle ADB is taken as 90° .Give reasons.

Answer 1

angle subtended by diameter to any point on circumference is 90

therefore ADB = 90

Answer 2

here is answer take the following step( s) into consideration !!!

as we know that angle made by diameter in a circle is 90°

for clarification look this attachment :-


or it have simple logic ;-

that => < ACB = 2 <AOB