Triangle is isosceles with and Point is inside the triangle so that and . Find the measure of in degrees.
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Let ∠ C M B = θ . Using Sine Rule, we have:
△ A C M : △ B C M : sin ∠ M A C C M = sin ∠ C M A A C ⇒ sin 7 ∘ C M = sin ∠ C M A A C ⇒ C M = sin 1 5 0 ∘ A C sin 7 ∘ = sin 3 0 ∘ A C sin 7 ∘ = 2 A C sin 7 ∘ sin ∠ M B C C M = sin ∠ C M B B C ⇒ sin ( 9 7 ∘ − θ ) C M = sin θ B C ⇒ C M = sin θ B C cos ( θ − 7 ∘ ) = sin θ A C cos ( θ − 7 ∘ )
⇒ 2 sin 7 ∘ 2 sin 7 ∘ sin θ 2 sin 7 ∘ sin θ cos 7 ∘ cos θ − sin 7 ∘ sin θ cos θ + 7 ∘ ⇒ θ + 7 ∘ ⇒ ∠ C M B = sin θ cos ( θ − 7 ∘ ) = cos ( θ − 7 ∘ ) = cos 7 ∘ cos θ + sin 7 ∘ sin θ = 0 = 0 = 9 0 ∘ = θ = 9 0 ∘ − 7 ∘ = 8 3 ∘