Question

in ∆abc ,prove that cos a = b^2 +c^2 -a^2/ 2 bc​

Answer 1

Step-by-step explanation:

bc cos²A/2 + ac cos²B/2 + a

b cos²C/2bc cos²A/2 + ac co

s²B/2 + ab cos²C/2bc cos²A

/2 + ac cos²B/2 + ab cos²C/2