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C H A P T E R 5 Analytic Trigonometry

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504 Chapter 5 <strong>Analytic</strong> <strong>Trigonometry</strong><br />

87.<br />

88.<br />

89.<br />

6x 2x 6x 2x<br />

2 sin<br />

2 cos<br />

2 0<br />

sin 4x 0 or cos 2x 0<br />

4x n or cos 2x <br />

n<br />

2<br />

x n<br />

4<br />

sin 6x sin 2x 0<br />

2 sin 4x cos 2x 0<br />

n<br />

or cos 2x <br />

4 2<br />

In the interval we have<br />

x 0, 3 5 3 7<br />

, , , , , ,<br />

4 2 4 4 2 4 .<br />

0, 2<br />

2 sin 4x sin2x 0<br />

sin 4x 0<br />

0<br />

2<br />

−2<br />

cos 2x cos 6x 0<br />

2 sin 4x sin 2x 0<br />

4x n<br />

x n<br />

4<br />

hx cos 2x cos 6x<br />

x 0, 3 5 3 7<br />

, , , , , ,<br />

4 2 4 4 2 4<br />

cos 2x<br />

1<br />

sin 3x sin x<br />

cos 2x<br />

1<br />

2 cos 2x sin x<br />

2 sin x 1<br />

sin x 1<br />

2<br />

x 5<br />

,<br />

6 6<br />

2<br />

or<br />

0<br />

2<br />

−2<br />

sin 2x 0<br />

2x n<br />

x n<br />

2<br />

2<br />

x 0, 3<br />

, ,<br />

2 2<br />

cos 2x<br />

1 0 90.<br />

sin 3x sin x<br />

0<br />

1<br />

−1<br />

0<br />

2<br />

−2<br />

sin 3x sin xsin 3x sin x 0<br />

2 sin 2x cos x2 cos 2x sin x 0<br />

sin 2x 0 ⇒ x 0, 3<br />

, ,<br />

2 2 or<br />

cos x 0 ⇒ x 3<br />

,<br />

2 2 or<br />

cos 2x 0 ⇒ x 3 5 7<br />

, , ,<br />

4 4 4 4 or<br />

sin x 0 ⇒ x 0, <br />

2<br />

2<br />

sin 2 3x sin 2 x 0<br />

fx sin 2 3x sin 2 x

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