Radians & Degrees REVIEW

A radian is a unit of angular measure defined as the angle subtended at the center of a circle by an arc equal in length to the radius of the circle.

To convert degrees to radians, multiply the degree measure by $$\frac{\text{π}}{180}$$ .

To convert radians to degrees, multiply the radian measure by $$\frac{180}{\text{π}}$$ .

The reference angle is the acute angle formed by the terminal side of an angle and the x-axis.

For an angle in radians, subtract or add $$\text{π}$$ or $$2\text{π}$$ to find the equivalent angle in the first rotation, then find the acute angle with the x-axis.

The reference angle for $$\frac{5\text{π}}{6}$$ is $$\frac{\text{π}}{6}$$ .

The sine of $$\frac{3\text{π}}{2}$$ is -1.

The cosine of $$\frac{2\text{π}}{3}$$ is - $$\frac{1}{2}$$ .

$$\frac{5\text{π}}{4}$$ is located in Quadrant III.

The tangent of $$\frac{5\text{π}}{6}$$ is - $$\frac{1}{\text{√3}}$$ .