Question

The points A(0, 0), B(cosα, sinα) and C(cosβ , sinβ) are the vertices of a right angled triangle if

(a) \(sin(\frac{\alpha + \beta}2) = \frac1{\sqrt 2}\)

(b) \(cos(\frac{\alpha + \beta}2) = \frac1{\sqrt 2}\)

(c) \(cos(\frac{\alpha - \beta}2) = \frac1{\sqrt 2}\)

(d) \(sin(\frac{\alpha + \beta}2) =- \frac1{\sqrt 2}\)

Answer 1

Correct option is (c) \(cos(\frac{\alpha - \beta}2) = \frac1{\sqrt 2}\)