By solving L.H.S. of the equation :
⇒1 - cot Atan A+1 - tan Acot A⇒1−tan A1tan A+1 - tan Atan A1⇒tan Atan A - 1tan A+tan A(1 - tan A)1⇒tan A - 1tan2A+tan A(1 - tan A)1⇒tan A - 1tan2A−tan A(tan A - 1)1⇒tan A(tan A - 1)tan3A−1⇒tan A(tan A - 1)(tan A - 1)(tan2A+ tan A + 1)⇒tan Atan2A+ tan A + 1⇒tan Atan2A+tan Atan A+tan A1⇒tan A + 1 + cot A⇒cos Asin A+1+sin Acos A⇒sin A cos Asin2A+sin A cos A + cos2A.
By formula,
sin2 A + cos2 A = 1
⇒sin A cos A1+sin A cos A⇒⇒sin A cos A1+sin A cos Asin A cos A⇒cosec A sec A+1.
Since, L.H.S. = R.H.S.
Hence, proved that 1 - cot Atan A+1 - tan Acot A = sec A cosec A + 1.