Forced by an Identity

Problem

In △ABC\triangle ABC,

3sin⁡2B+7sin⁡2C=2sin⁡Asin⁡Bsin⁡C+2sin⁡2A.3\sin^2 B + 7\sin^2 C = 2\sin A\sin B\sin C + 2\sin^2 A.

Find sin⁡(A+π4)\sin\left(A + \dfrac{\pi}{4}\right).

Answer

Solution

Difficulty7/10
TopicsLaw of Sines, trigonometry, Law of Cosines, AM-GM, Triangle Geometry

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