find the cosine and sine of 210 degrees round your answers to the nearest hundredth if necessary.

This can be answered by understanding the unit circle and the Pythagorean theorem. 210° can form a right triangle with the x-axis in quadrant III. To get the value of the angle formed between the circle’s radius and the x-axis, divide the angles of the 2 quadrants from 210°.
210°-90-°90° = 30°
In the Pythagorean theorem has a ratio of 1,2, √3 of the sides of the triangle. In a unit circle, the opposite side from the 30° angle is 1. The adjacent side is √3 while the hypotenuse is 2. With this info, we can use SOHCAHTOA.
So,
Sin(∅) = opposite / hypotenuse
Sin(30°) = ½ =0.5
Cos(∅) = adjacent/hypotenuse
Cos(30°) = sqrt.3/2 = 0.86602 = 0.87

The correct answer is c