Question 143

What is the value of $$\frac{\cos x+cos y}{sinx + siny}$$ ?

Solution

Expression : $$\frac{\cos x+cos y}{sinx + siny}$$

= $$\frac{cos(\frac{x+y}{2})cos(\frac{x-y}{2})}{sin(\frac{x+y}{2})cos(\frac{x-y}{2})}$$

= $$\frac{cos(\frac{x+y}{2})}{sin(\frac{x+y}{2})}$$

= $$cot(\frac{x+y}{2})$$

=> Ans - (D)

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