Question

prove that:tan1tan11tan21tan69tan79tan89=1

Answer 1

Step-by-step explanation:

LHS = tan 1° tan 11° tan 21° tan 69° tan 79° tan 89°

= tan ( 90° - 1° ) tan ( 90° - 11°) tan ( 90° - 21° ) tan 69° tan 79° tan 89°

= cot 89° cot 79° cot 69° tan 69° tan 79° tan 89°

= 1

= RHS

hence it's proved...