In Fig. 16.120, O is the centre of the circle. If APB=50°, find AOB and OAB.

APB = 50o (Given)

By degree measure theorem,


AOB = APB


APB = 2 * 50


= 100o


Since,


OA = OB (Radii)


Hence,


OAB = OBA (Angle opposite to equal sides are equal)


Let,


OAB = x


In Triangle OAB,


OAB + OBA + AOB = 180o


x + x + 100o = 180o


2x = 80o


x = 40o


OAB = OBA = 40o


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