Radians and Reference Angles

Reference Angle

Reference Angle

• Measure of Terminal side to closest x axis

• Distance to x axis

• MUST be < 90 degree

• MUST be Positive

Finding Reference Angles

• The blue portion of graph is the original angle

• The red portion is reference angle

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Finding Reference angle by Quadrant

• Quadrant 1 - itself

• Quadrant 2 - 180 Degrees minus the angle

• Quadrant 3 - The angle minus 180 degrees

• Quadrant 4 - 360 minus the angle

Multiple Choice

What is the reference angle?

• 112

• 68

• 158

• 248

Multiple Choice

What is the reference angle?

• 43

• -43

• 47

• -47

Multiple Choice

What is the reference angle for 63°?

• 117°

• 207°

• 63°

• 153°

Multiple Choice

What is the reference angle for -30°?

• 150°

• 30°

• 80°

• 60°

Multiple Choice

What is the reference angle for 125°?

• 235°

• 125°

• 75°

• 55°