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.

- 2 + 10x³ - 21x² + 19x - 4

step-by-step explanation:

each term in the second factor is multiplied by each term in the first factor

x²(- 2x² + 4x - 1) - 3x(- 2x² + 4x - 1) + 4(- 2x² + 4x - 1) ← distribute

= - 2 + 4x³ - x² + 6x³ - 12x² + 3x -8x² + 16x - 4

collect like terms

= - 2 + 10x³ - 21x² + 19x - 4 ← in standard form