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Mathematics

Find the magnitude of angle A, if :

2 sin A cos A - cos A - 2 sin A + 1 = 0

Trigonometric Identities

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Answer

2 sin A cos A - cos A - 2 sin A + 1 = 0

⇒ (2 sin A cos A - cos A) - (2 sin A - 1) = 0

⇒ cos A(2 sin A - 1) - 1(2 sin A - 1) = 0

⇒ (2 sin A - 1)(cos A - 1) = 0

⇒ (2 sin A - 1) = 0 or (cos A - 1) = 0

⇒ 2 sin A = 1 or cos A = 1

⇒ sin A = 12\dfrac{1}{2} or cos A = 1

⇒ sin A = sin 30° or cos A = cos 0°

⇒ A = 30° or 0°

Hence, A = 30° or 0°.

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