Evaluating Cosine Using A Table

Question

Using the unit circle values provided in the table above, evaluate $$\cos(3*\pi/4)$$.
 
| Angle (radians) | Cosine                          | Sine                           |
|-----------------|---------------------------------|--------------------------------|
| $$\pi/4$$      | $$\frac{\sqrt{2}}{2}$$         | $$\frac{\sqrt{2}}{2}$$         |
| $$3\pi/4$$     | $$-\frac{\sqrt{2}}{2}$$        | $$\frac{\sqrt{2}}{2}$$         |
| $$\pi/6$$      | $$\frac{\sqrt{3}}{2}$$         | $$\frac{1}{2}$$               |
| $$5\pi/6$$     | $$-\frac{\sqrt{3}}{2}$$        | $$\frac{1}{2}$$               |

Accepted Answer

$$-\frac{\sqrt{2}}{2}$$

Answer

$$-\frac{1}{2}$$

Answer

$$\frac{1}{2}$$

Answer

$$\frac{\sqrt{2}}{2}$$

Rank	User	Correct Count	Attempt Count	Time	Score
#1	fahidalia08	2	2	0m 19s	181
#2	mihikadarbha	2	2	0m 38s	162
#3	germaingutierrez753	1	1	0m 00s	100
#4	andrew.hsia9	1	1	0m 04s	96
#5	mahmoudjibrin08	1	1	0m 04s	96
#6	majk30881	1	1	0m 04s	96
#7	sanvirrao12	1	1	0m 10s	90
#8	vaibhav.vemuri	1	1	0m 11s	89
#9	chunxiangxu.cxu	1	1	0m 11s	89
#10	hekim4066	1	1	0m 13s	87

Angle (radians)	Cosine	Sine
$$\pi/4$$	$$\frac{\sqrt{2}}{2}$$	$$\frac{\sqrt{2}}{2}$$
$$3\pi/4$$	$$-\frac{\sqrt{2}}{2}$$	$$\frac{\sqrt{2}}{2}$$
$$\pi/6$$	$$\frac{\sqrt{3}}{2}$$	$$\frac{1}{2}$$
$$5\pi/6$$	$$-\frac{\sqrt{3}}{2}$$	$$\frac{1}{2}$$

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