Question

evaluate trig values of quadrant angles in degree
use unit circle to evalu
14 multiple choice 1 point
evaluate the trigonometric function of the given quadrantal angle.
cos 1620°
1
0
-1
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15 multiple choice 1 point
evaluate the trigonometric function of the given quadrantal angle.

Explanation:

Step1: Find the coterminal angle

Since the cosine function has a period of \(360^{\circ}\), we can find a coterminal angle of \(1620^{\circ}\) by subtracting multiples of \(360^{\circ}\).

$$1620\div360 = 4.5$$

$$1620-4\times360=1620 - 1440=180^{\circ}$$

Step2: Evaluate \(\cos180^{\circ}\)

On the unit - circle, for an angle \(\theta = 180^{\circ}\), the coordinates of the point on the unit - circle are \((x,y)=(- 1,0)\). And by the definition of the cosine function \(\cos\theta=x\). So, \(\cos180^{\circ}=-1\)

Answer:

-1