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Show that sin 100° – sin 10° is positive. |
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Answer» Suppose f(x) = sin 100° – sin 10° On dividing and multiplying by √(12 + 12) i.e. by √2, f(x) = √2(1/√2 sin 100° – 1/√2 sin 10°) f(x) = √2(cos π/4 sin (90 + 10)° – sin π/4 sin 10°) (since, 1/√2 = cos π/4 and 1/√2 = sin π/4) f(x) = √2(cos π/4 cos 10° – sin π/4 sin 10°) As we know that cos A cos B – sin A sin B = cos (A + B) f(x) = √2 cos (π/4 + 10°) |
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