Cosine Rule

Question 0

Find missing angle

Answer 0

a’ - b’ - c’ = -2bc*cosA

CosA = a' - b' - c'
            \_\_\_\_\_\_\_\_\_
                -2bc
          = b' + c' - a' 
             \_\_\_\_\_\_\_\_\_
                  2bc

Question 1

To find missing side

Answer 1

a’ = b’ + c’ -2bc*cosA