Prove that:

Cross multiplying we get,

Cot A . cos A . cot A . cos A = (cot A + cos A) (cot A – cos A)

Cot²A . cos²A = (Cot²A – cos²A)

[By applying : (a + b)(a – b) = a²– b²]

Taking R.H.S = (Cot²A – cos²A)

= Cot²A . cos²A = L.H.S

Hence, Proved.