Q21 of 143 Page 6

The value of tan 10° tan 15° tan 75o tan 80. is

Given,


tan 10° tan 15° tan 75o tan 80°


As we know,


tan (90 – θ) = than θ


Therefore,


⇒ tan (90°-80°) tan (90°-75°) tan 75o tan 80°


⇒ cot 80° cot 75° tan 75° tan 80°


⇒ (cot 80° tan 80°) (cot 75° tan 75°)……… [ cot θ = 1/tanθ ]


⇒


⇒ (1)(1) = 1

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