In-a-triangle-ABC-a-b-cos-C-c-cos-B-

Question Number 90535 by 1223 last updated on 24/Apr/20

In a triangle A B C, a (b \cos C - c \cos B) =

Answered by $@ty@m123 last updated on 24/Apr/20

a (b \times \frac{a^{2} + b^{2} - c^{2}}{2 a b} - c \times \frac{c^{2} + a^{2} - b^{2}}{2 c a})

a (\frac{a^{2} + b^{2} - c^{2}}{2 a} - \frac{c^{2} + a^{2} - b^{2}}{2 a})

\frac{1}{2} (a^{2} + b^{2} - c^{2} - c^{2} - a^{2} + b^{2})

\frac{1}{2} (2 b^{2} - 2 c^{2})

b^{2} - c^{2}