Expression : (cotAcotB + 1) / (cotB - cotA) = x
= $$(\frac{cos A cos B}{sin A sin B} + 1) \div (\frac{cos B}{sin B} - \frac{cos A}{sin A})$$
= $$(\frac{cos Acos B + sin Asin B}{sin Asin B}) \div (\frac{sin Acos B - cos Asin B}{sin Asin B})$$
= $$[\frac{cos(A - B)}{sin A sin B}] \div [\frac{sin(A - B)}{sin A sin B}]$$
= $$[\frac{cos(A - B)}{sin A sin B}] \times [\frac{sin A sin B}{sin(A - B)}]$$
= $$\frac{cos(A - B)}{sin(A - B)} = cot(A - B)$$
=> Ans - (B)
Create a FREE account and get: