Unit: More Trig Functions
Converting between Degrees and Radians:
Radian: the measure of an angle that, when drawn as a central angle of a circle, would intercept an arc whose length is equal to the length of a radius of the circle.
measure.radian in anglean of examplean is 3
Lets determine how many degrees are in 1 radianβ¦
How many degrees are there once around a circle?
360
In radians, once around the circle is
360 Β°=2π πππππππ 360 Β°
2=
2π πππππππ 2
180 Β°=ππππππππ 180 Β°π
=π πππππππ
Ο
180 Β°π
=1ππππππ OR
It may be necessary to convert from radian measure to degree measure.
radians toDegrees 2. degrees toRadians 1.
know. toneed that wesconversion twoare There
Radians to degrees:
.180
by anglegiven the
multiply wedegrees, toradians convertingWhen
Change each angle from radian measure to degree measure.
2
3 .11
180
2
3 .expression hesimplify t
and thecancelcan weso thisdo We
2
1803
2
540 270 270 radians
2
3
Page 1
13.5π4
5π4β180πΒΏ
5 β1804
ΒΏ900
4ΒΏ225
15.5π6
5π6β180πΒΏ
5 β1806
ΒΏ900
6ΒΏ150
17.π5
π5β
180πΒΏ
1805 ΒΏ36
19.βπ6β
π6β180πΒΏβ
1806 ΒΏβ30
Degrees to radians:
.180
by angle given the
multiply weradians, todegrees converting When
Change each angle from degree measure to radian measure.
1. 120 120 βπ
180ΒΏ
120π180
We need to simplify this fraction by using the calculator.
ΒΏ2π3
Notice that we keep in the final answer
Page 1
3.β50 β50 βπ
180ΒΏβ50π
180ΒΏβ5π
18
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5.β135β135 βπ
180ΒΏβ135π
180ΒΏβ3π
4
7. 330 330 βπ
180ΒΏ
330π180
ΒΏ11π
6
9.β45β45 βπ
180ΒΏβ45π
180ΒΏβπ
4
Finding the measure of an arc on a circle.
π =π πThis formula is used when trying to find one of three things:
To use this formula, the measure of the central angle MUST BE IN RADIANS.
Page 1
21. Find the length of the radius of a circle in which a central angle of 4.5 radians intercepts an arc of 9 meters.
π =π π Is the central angle in radians?
9=π ( 4.5 )9
4.5=π ( 4.5 )
4.5
2=π
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21. What is the measure of an angle formed by the hands of a clock at 5:00?
a. degrees?b. radians?
2560
=π₯
360
6 0π₯=9000
6 0 π₯60
=900060
π₯=150
2560
=π₯
2π
6 0π₯=50π
6 0 π₯60
=50π60
π₯=5π6
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27. Circle O has a radius of 10 inches. What is the length, in inches, of the arc subtended by a central angle measuring 2.5 radians?
1 0π=2.5
π π’ππ‘πππ
πππππ
π =π π
π =(10 ) (2.5 )π =25
21. Find the radius of a circle on which a central angle measuring 135 intercepts an arc on the circle with a length of 24 yds. [Answer may be expressed in terms of ]
Page 2
π =π π
24=π β135
24=π β135 βπ
180
24=π3π4
43π
β24=π3π4β
43π
32π
=π
Homework
Page 1#2-20 even, 26,28,29,30