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Problem
Problem
Explain why: a. - a
cos
400
∘
=
cos
40
∘
\cos 400^\circ = \cos 40^\circ
cos
40
0
∘
=
cos
4
0
∘
b. - b
sin
5
π
7
=
sin
19
π
7
\sin \frac{5\pi}{7} = \sin \frac{19\pi}{7}
sin
7
5
π
=
sin
7
19
π
c. - c
tan
13
π
8
=
tan
(
−
11
π
8
)
\tan \frac{13\pi}{8} = \tan \left(-\frac{11\pi}{8}\right)
tan
8
13
π
=
tan
(
−
8
11
π
)
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