If cos y = x cos (a + y), with cos a ≠ ± 1, prove that

Question

If cos y = x cos (a + y), with cos a &ne; &plusmn; 1, prove that

Philoid · Accepted Answer

Given, cos y = x cos (a + y)

Differentiating both sides with respect to x

⇒

⇒ …………..(I)

Since, cos y = x cos (a + y) ⇒ x = cos y/cos (a + y)

Substituting the value of x in (I)

⇒

Hence, proved