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cot 15°. cot 20°. cot 70°. cot 75° is equal to?
- A-1
- B0
- C1
- D2
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CCommunity
cot 15°. cot 20°. cot 70°. cot 75°
= cot 15° cot 20°.tan (90° - 70°).tan (90° - 75°)
[As we know tan (90° - θ) = cotθ]
= cot 15°.cot 20°.tan 20°.tan 15°
= (cot 15°.tan 15°) (cot 20°.tan 20°) [cotθ.tanθ = 1]
= 1 × 1 = 1
= cot 15° cot 20°.tan (90° - 70°).tan (90° - 75°)
[As we know tan (90° - θ) = cotθ]
= cot 15°.cot 20°.tan 20°.tan 15°
= (cot 15°.tan 15°) (cot 20°.tan 20°) [cotθ.tanθ = 1]
= 1 × 1 = 1