EXAMPLE 3
Find reference angles
Find the reference angle
θ'
for (
a
)
θ
=
5π
3
and
(
b
)
θ
=
– 130
°
.
SOLUTION
a.
The terminal side of
θ
lies in Quadrant IV.
So,
θ'
= 2π
–
.
5π
3
π
3
=
b.
Note that
θ
is coterminal with
230°,
whose terminal
side lies in Quadrant III. So,
θ'
= 230° –
180° + 50°.