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Given sin(theta) = -8/17 and pi (Picture of the problem below) (answers in picture below)

Given sin(theta) = -8/17 and pi (Picture of the problem below) (answers in picture-example-1
User Erajuan
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1 Answer

7 votes

Answer:

(d) 240/289

Explanation:

The trig identity for the sine of a double angle can be used to find the desired value.

sin(2θ) = 2sin(θ)cos(θ)

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The cosine of this 3rd-quadrant angle is negative:

cos(θ) = -√(1 -(-8/17)²) = -(√(289 -64))/17 = -15/17

Then the desired sine value is ...

sin(2θ) = 2(-8/17)(-15/17) = 240/289

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Additional comment

The attached calculator result comes from the principal value of the arcsine function resulting in a 4th-quadrant angle for negative sine values. Double that angle will still be a 4th-quadrant angle. When the translation is made to the appropriate quadrant, the desired double angle will be a 1st-quadrant angle with a positive sine.

Given sin(theta) = -8/17 and pi (Picture of the problem below) (answers in picture-example-1
User Mushfiq
by
6.3k points