Solve the following equations on the interval x E [0, 2π]. Give exact solutions.
a. 5 sin x + 1 = 3 sin x
b. 2 cos² x + cos x - 1 = 0
c. -2 cos 2x = 2 sin x
d. csc(2x) = -2 / √3

Respuesta :

The solution to the equations in the interval of (0, 2•π) are;

a. [tex]x = \frac{11 \cdot \pi }{6} [/tex]

b. [tex]x = \frac{\pi }{3} [/tex]

c. [tex]x = \frac{7 \cdot \pi }{6} [/tex][tex]x = \frac{11 \cdot \pi }{6} [/tex]

d. [tex]x = \frac{2 \cdot \pi }{3} [/tex]

[tex]x = \frac{ 5\cdot \pi }{6} [/tex]

How can trigonometric functions be evaluated?

The trigonometric functions can be expressed as follows;

a. 5•sin(x) + 1 = 3•sin(x)

5•sin(x) - 3•sin(x) = -1

2•sin(x) = -1

sin(x) = -1/2

The values of x are therefore;

[tex]x = - \frac{12 \cdot \pi \cdot n1 -7 \cdot \pi }{6} [/tex]

[tex]x = \frac{12 \cdot \pi \cdot n1 - \pi }{6} [/tex]

Which gives;

[tex]x = \frac{11 \cdot \pi }{6} [/tex]

b. 2•cos²(x) + cos(x) - 1 = 0

Factoring gives;

(2•cos(x) - 1)•(cos(x) + 1) = 0

2•cos(x) - 1 = 0

cos(x) = 1/2

Therefore;

[tex]x = - \frac{6 \cdot \pi \cdot n1 + \pi }{3} [/tex]

Which gives;

[tex]x = \frac{\pi }{3} [/tex]

c. -2•cos (2•x) = 2•sin (x)

-cos (2•x) = sin(x)

cos (2•x) = 1 - 2•sin²(x)

-(1 - 2•sin²(x)) - sin(x) = 0

2•sin²(x) - sin(x) - 1 = 0

(2•sin(x) + 1)•(sin(x) - 1) = 0

sin(x) = -1/2

[tex]x = - \frac{12 \cdot \pi \cdot n1 -7 \cdot \pi }{6} [/tex]

Which gives;

[tex]x = \frac{7 \cdot \pi }{6} [/tex]

Second part;

[tex]x = \frac{12 \cdot \pi \cdot n1 - \pi }{6} [/tex]

Which gives;

[tex]x = \frac{11 \cdot \pi }{6} [/tex]

d. csc(2•x) = -2/√3

sin(2•x) = -√3/2

Therefore;

[tex]x = - \frac{3 \cdot \pi \cdot n1 -2 \cdot \pi }{3} [/tex]

[tex]x = \frac{6 \cdot \pi \cdot n1 - \pi }{6} [/tex]

The values of x are;

[tex]x = \frac{2 \cdot \pi }{3} [/tex]

[tex]x = \frac{ 5\cdot \pi }{6} [/tex]

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