In a triangle ,

MATHEMATICS · Single correct · A Level · Mathematics · Trigonometry · Trigonometry

Problem

In a triangle ABCABC, a2cos⁡2B+b2cos⁡2A+2abcos⁡(A−B)=a^2\cos2B+b^2\cos2A+2ab\cos(A-B)= (1) a2a^2 (2) c2c^2 (3) b2b^2 (4) a2+b2a^2+b^2

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