Mathematics
Express the following in terms of trigonometric ratios of angles between 0° to 45° :
tan 81° + cos 72°
Trigonometrical Ratios
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Answer
Solving,
⇒ tan 81° + cos 72°
⇒ tan (90° - 9°) + cos (90° - 18°)
As, tan(90° - θ) = cot θ, cos(90° - θ) = sin θ
⇒ cot 9° + sin 18°.
Hence, tan 81° + cos 72° = cot 9° + sin 18°.
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