1.

Prove that in any △ABC, cos A=b2+c2−a22bc, where a, b and c are the magnitudes of the sides opposite to the vertices A, B and C, respectively.

Answer»

Prove that in any ABC, cos A=b2+c2a22bc, where a, b and c are the magnitudes of the sides opposite to the vertices A, B and C, respectively.



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