The LAW of COSINES is used to solve oblique triangles in which two sides and the included angle (SAS)are given or three sides (SSS) are given.

Question

For any ∆𝐀𝐁𝐂 with angle measures A, B, C and side lengths a, b, c

STANDARD FORM
a²= b²+c²-2bcCos A
b = a²+c²-2acCos B
c²=a²+b²-2abCos C

Answer 1

thanks for that important information, but your second version of the
equation contains a typo, making it incorrect.