Find the Exact Value of the Cosine of 675 Degrees Using the Unit Circle

The angle 675 degrees is not located on the unit circle as it is larger than one revolution. The trigonometric functions of coterminal angles are equal. An angle that is coterminal to 675° but on the unit circle is found by subtracting 360° from the given angle. The x coordinate of this angle is then equal to the cosine of 675°. (A calculator would only give a numerical approximation.)

Timestamps
0:00 Introduction
0:40 Coterminal Angles
1:55 Cos(675 Degrees)