In $ riangleABC$ if$\alpha=90^{\circ}$ then according to law of cosine the value of the square of the side a is defined as

Question

Accepted Answer

$a^{2}=b^{2}+c^{2}$

Answer

$a^{2}=a^{2}+c^{2}+2ac$

Answer

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

Answer

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