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 them according to law of cosine, the value of $cosine \beta$ is defined as:

Question

Accepted Answer

$\cos\beta=\frac{c^{2}+a^{2}-b^{2}}{2ac}}$

Answer

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

Answer

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

Answer

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