Recall the definition: Let θ be an angle in standard position. Its reference angle is the acute angle θ′ formed by the terminal side of θ and the horizontal axis.

Question

Below, express  in the same units (degrees or radians) as theta. You can enter arithmetic expressions like 210-180 or 3.5-pi. 

1. The reference angle of 100 deg is _____
2. the reference angle of 350 deg is _____
3. the ref angle of 4 is ______

HINT: draw the angle.

Answer 1

100° lies in Quadrant 2. Reference angle = 180° - 100° = 80°

350° lies in quadrant 4. Reference angle = 360° - 350° = 10°

4 radians lies in quadrant 3. Reference angle = 4 - π = 0.858 radians