Question

If a + b equal to pi by 4 then prove that 1 + cot a into 1 + cot B equal to 2 into cot a into cot b​

Answer 1

(cotA − 1) (cotB − 1) = 2

Explanation:

A+B= π/4 = 180°/4 = 45°

A+B=45°

∴ cot(A+B)=cot45°

∴ cotBcotA−1 / (cotB+cotA) = 1

⇒cotB + cotA = cotBcotA = 1

⇒cotB + cotA − cotBcotA + 1 = 0

⇒cotBcotA − cotB − cotA − 1 = 0

⇒cotBcotA − cotB − cotA − 1 + 2 = 0+2

⇒cotBcotA − cotB − cotA + 1 = 2

⇒cotB(cotA − 1) (cotA − 1) = 2

⇒(cotA − 1) (cotB − 1) = 2

Proved