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How To Find The Reference Angle In Radians and Degrees - Trigonometry

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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 Trigonometry - Free Formula Sheet: https://www.video-tutor.net/formula-sheets.html Trigonometry Video Lessons: https://www.video-tutor.net/basic-trigonometry.html Final Exam and Test Prep Videos: https://bit.ly/41WNmI9
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Video Transcript

0:01
now let's talk about reference angles
0:03
and how to find them
0:06
so let's say if we have an angle
0:09
of 120 degrees
0:12
what is the reference angle
0:15
so let's draw 120 degrees 120
0:18
is in quadrant two
0:23
so this is 120 relative to the positive
0:26
x-axis
0:27
the reference angle
0:29
is the angle between the x-axis
0:33
and the terminal side or the terminal
0:34
array
0:35
and it's always less than 90. it's
0:37
between 0 and 90.
0:39
so what is the angle here
0:43
to find that angle we know it's
0:46
if this angle is 180
0:48
and this is 120 it has to be the
0:50
difference between the two
0:51
so it's 180 minus
0:54
120
0:55
so this angle is 60 and that's the
0:57
reference angle
0:59
so let's try another example what is the
1:01
reference angle
1:03
for an angle that's 210 relative to
1:05
positive x-axis
1:08
so this is 210
1:12
and we know the negative x-axis is 180.
1:14
so the difference is 30.
1:17
so the reference angle is always between
1:19
a terminal ray and the x-axis
1:23
now there are some equations that you
1:25
can use to easily find the reference
1:27
angle
1:29
so anytime you have an angle in quadrant
1:32
one the reference angle
1:34
is equal to the angle in quadrant one
1:38
if you have an angle in quadrant two the
1:40
reference angle
1:42
is going to be 180 minus the angle in
1:45
quadrant two
1:47
if the angle is in quadrant three
1:50
the reference angle
1:51
is going to be the angle in quadrant
1:53
three minus 180
1:56
now if the angle is in quadrant four
1:58
then it's going to be 360 minus the
2:01
angle in quadrant four
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