Question

In the figure O is the centre and <AOB=80
A) find<ACB
B)WHAT IS THE MEASURE OF <ADB​

Answer 1

Answer:

Angle ACB = 40° {by diameter theorem}

and angle ADB = 140°( since sum of opposite angle is 180°)

Answer 2

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A) /_ACB = 1/2 × /_AOB = 1/2 × 80° = 40°

( angle subtended at the centre by an arc is double the angle subtended on remaining arc ).

B) /_ACB + /_ADB = 180° (Cyclic quadrilateral)

40° + /_ADB = 180°

/_ADB = 180° - 40° = 140°.