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Question
Evaluate:
3 cos 80° cosec 10°+ 2 sin 59° sec 31°
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Solution
3 cos 80° cosec 10° + 2 sin 59° sec 31°
= 3 cos 80° cosec (90° – 80°) + 2 sin 59° sec (90° – 59°)
= 3 cos 80° sec 80° + 2 sin 59° cosec 59°
= 3 × 1 + 2 × 1 ...(∵ cos A × sec A = 1)
= 3 + 2
= 5
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