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How To Find The Reference Angle In Radians and Degrees - Trigonometry
                    
                    This trigonometry video tutorial provides a basic introduction into reference angles.  It explains how to find the reference angle in radians and degrees.  
Trigonometry Final Exam Review:     https://www.youtube.com/watch?v=OAsbx4TEnL0
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Video Transcript
now let's talk about reference angles
                                    and how to find them
                                    so let's say if we have an angle
                                    of 120 degrees
                                    what is the reference angle
                                    so let's draw 120 degrees 120
                                    is in quadrant two
                                    so this is 120 relative to the positive
                                    x-axis
                                    the reference angle
                                    is the angle between the x-axis
                                    and the terminal side or the terminal
                                    array
                                    and it's always less than 90. it's
                                    between 0 and 90.
                                    so what is the angle here
                                    to find that angle we know it's
                                    if this angle is 180
                                    and this is 120 it has to be the
                                    difference between the two
                                    so it's 180 minus
                                    120
                                    so this angle is 60 and that's the
                                    reference angle
                                    so let's try another example what is the
                                    reference angle
                                    for an angle that's 210 relative to
                                    positive x-axis
                                    so this is 210
                                    and we know the negative x-axis is 180.
                                    so the difference is 30.
                                    so the reference angle is always between
                                    a terminal ray and the x-axis
                                    now there are some equations that you
                                    can use to easily find the reference
                                    angle
                                    so anytime you have an angle in quadrant
                                    one the reference angle
                                    is equal to the angle in quadrant one
                                    if you have an angle in quadrant two the
                                    reference angle
                                    is going to be 180 minus the angle in
                                    quadrant two
                                    if the angle is in quadrant three
                                    the reference angle
                                    is going to be the angle in quadrant
                                    three minus 180
                                    now if the angle is in quadrant four
                                    then it's going to be 360 minus the
                                    angle in quadrant four
                                    

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