Question -
Answer -
Let us consider LHS:
We can observe that we can get terms c тАУ b cos A and bтАУ c cos A from projection formula
From projection formula we get,
c = a cos B + b cos A
c тАУ b cos A = a cos B тАж. (i)
And,
b = c cos A + a cos C
b тАУ c cos A = a cos C тАж. (ii)
Dividing equation (i) by (ii), we get,
= RHS
Hence proved.