L4 Reference Angles

Front

What is a reference angle?

Back

A reference angle is the acute angle formed by the terminal side of an angle in standard position and the x-axis.

Front

How do you find the reference angle for a negative angle?

Back

To find the reference angle for a negative angle, first add 360° (or 2π radians) to the angle until it is positive, then find the reference angle as you would for a positive angle.

Front

What is the reference angle for -310°?

Back

50°.

Front

What is the reference angle for 63°?

Back

63°.

Front

How do you determine the reference angle for angles greater than 360°?

Back

Subtract 360° (or 2π radians) from the angle until it is within the range of 0° to 360° (or 0 to 2π radians), then find the reference angle.

Front

What is the reference angle for π/4 radians?

Back

π/4 radians.

Front

What is the reference angle for 73°?

Back

73°.

Front

Are -3π/4 and 5π/4 coterminal angles?

Back

Yes, they are coterminal angles because they differ by a multiple of 2π.

Front

What is the formula to find the reference angle in the second quadrant?

Back

Reference angle = 180° - θ (or π - θ in radians).

Front

What is the formula to find the reference angle in the third quadrant?

Back

Reference angle = θ - 180° (or θ - π in radians).