Q20 of 100 Page 17

If A, B, C are three points on a circle with centre O such that ∠AOB=90° and ∠BOC=120°, then ∠ABC=

∠BOC = 120°

∠AOC = ∠AOB + ∠BOC


= 90o + 120o


= 210°


Now,


∠ABC = * (Reflex ∠AOC)


= (360o – 210o)


= 75°

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