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If cos θ = -0.6, and 180° < θ < 270°, find the exact value of sin 2θ.

1 Answer

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Answer:

sin(2θ) = 0.96

Explanation:

In the third quadrant, both sin(θ) and cos(θ) are negative. Then the double-angle trig identity tells us ...

sin(2θ) = 2·sin(θ)·cos(θ) = -2cos(θ)√(1 -cos(θ)²) . . . . using the negative root

Filling in the given value, we have

sin(2θ) = -2·(-0.6)(√(1-(-0.6)²) = 2·0.6·0.8 = 0.96

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