Statement I: If

MATHEMATICS · Subjective · A Level · Mathematics · Trigonometry · Trigonometry

Problem

Statement I: If, in a triangle ABCABC, sin⁡2A+sin⁡2B+sin⁡2C=2\sin^2A+\sin^2B+\sin^2C=2, then one of the angles must be 90∘90^\circ. Statement II: In any triangle ABCABC, cos⁡2A+cos⁡2B+cos⁡2C=−1−4cos⁡Acos⁡Bcos⁡C.\cos2A+\cos2B+\cos2C=-1-4\cos A\cos B\cos C.

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