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In △ABC\triangle ABC, ∠A=90∘\angle A = 90^{\circ}, if tan⁡C=3\tan C = \sqrt{3}, then find the value of sin⁡B+cos⁡C−cos⁡2B\sin B + \cos C - \cos^2 B

Solution

✅ Correct Option: 2

tan⁡C=3  ⟹  C=60°\tan C = \sqrt{3} \implies C = 60°

Since A+B+C=180°A + B + C = 180°:

90°+B+60°=180°90° + B + 60° = 180°

B=30°B = 30°


sin⁡B+cos⁡C−cos⁡2B\sin B + \cos C - \cos^2 B

=sin⁡30°+cos⁡60°−cos⁡230°= \sin 30° + \cos 60° - \cos^2 30°

=12+12−(32)2= \dfrac{1}{2} + \dfrac{1}{2} - \left(\dfrac{\sqrt{3}}{2}\right)^2

=1−34= 1 - \dfrac{3}{4}

=14= \dfrac{1}{4}

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