Question

In triangle abc cos a = cosc.Cosb prove 2cotb.Cotc=1

Answer 1

A + B + C = 180 degrees
A = 180 – ( B + C )
cos A = cos B cos C
cos (180 – B – C) = cos B cos C
– cos ( B + C ) = cos B cos C
– cos B cos C + sin B sin C = cos B cos C
2 cos B cos C = sin B sin C
2 cot B cot C = 1

Hope it helps!

Answer 2

Step-by-step explanation:

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