Multiplying both sides of the given expression by (sec α – tan α) (sec β – tan β) (sec γ – tan γ), we get, 1.1.1 = (sec α – tan α) . (sec β – tan β). (sec γ – tan γ). tan α tan β tan γ ⇒ (sec α – tan α).(sec β – tan β).(sec γ – tan γ) = cot α.cot β.cot γ