Explain why sine of an angle greater than 180° and less than 360° is negative.

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Explanation:

The sine of an angle in standard position is the y-coordinate of the intersection of its terminal ray with the unit circle. When the angle is in the range 180° < θ < 360°, that point of intersection is in quadrant III or IV, where y-coordinates are negative.

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Alternative explanation:

That is where the sine curve is below the x-axis.

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