If $\alpha,\beta\:and\:\gamma$ are the measures of the angles of a triangle, and a, b and c are the lengths of sides opposite these angles, then according to law of cosine, the value of cosine $\alpha$ is defined as

Question

Accepted Answer

$\cos\alpha=\frac{b^{2}+c^{2}-a^{2}}{2bc}$

Answer

$\cos\alpha=\frac{a^{2}+b^{2}+2ab\cos\beta}{ab}$

Answer

$\cos\alpha=\frac{a^{2}+b^{2}-2ab\cos\beta}{ab}$

Answer

$\cos\alpha=\frac{a^{2}+b^{2}-c^{2}}{ab}$