Flashcard: Coterminal and Reference Angles

Coterminal angles are angles that share the same terminal side when drawn in standard position. They can be found by adding or subtracting multiples of 360° (or 2π radians).

A reference angle is the acute angle formed by the terminal side of an angle and the x-axis. To find it, subtract the angle from 180° (or π radians) if the angle is in the second quadrant, or subtract 360° (or 2π radians) if in the fourth quadrant.

The cosine of $$\frac{5\theta}{6}$$ is - $$\frac{\text{√3}}{2}$$ .

The sine of 45° is $$\frac{\text{√2}}{2}$$ .

They add up to 180 degrees.

Yes, they are coterminal angles.

The reference angle is 42°.

The sine of 30° is $$\frac{1}{2}$$ .

The cosine of 60° is $$\frac{1}{2}$$ .

The tangent of 45° is 1.