Solve the following equations for values of [tex]x[/tex] from [tex]0^{\circ}[/tex] to [tex]360^{\circ}[/tex] inclusive:

[tex]\[
\begin{array}{l}
14 \cos x + \cos 5x = 0 \\
15 \cos 4x - \cos x = 0 \\
16 \sin 3x - \sin x = 0 \\
18 \sin \left(x + 10^{\circ}\right) + \sin x = 0 \\
19 \cos \left(2x + 10^{\circ}\right) + \cos \left(2x - 10^{\circ}\right) = 0 \\
20 \cos \left(x + 20^{\circ}\right) - \cos \left(x - 70^{\circ}\right) = 0
\end{array}
\][/tex]



Answer :

To solve each trigonometric equation for [tex]\( x \)[/tex] in the range [tex]\( 0^\circ \)[/tex] to [tex]\( 360^\circ \)[/tex], we need to find the values of [tex]\( x \)[/tex] that satisfy each equation.

Let's address each equation one by one.

### Equation 1: [tex]\( 14 \cos x + \cos 5x = 0 \)[/tex]

The equation can be rewritten as:
[tex]\[ 14 \cos x + \cos 5x = 0 \][/tex]
We need to find values of [tex]\( x \)[/tex] where this equation holds true. After analyzing the behavior of this equation over the given domain, we find:

Solutions: [tex]\( x = 90^\circ \)[/tex] and [tex]\( x = 270^\circ \)[/tex]

### Equation 2: [tex]\( 15 \cos 4x - \cos x = 0 \)[/tex]

The equation can be rewritten as:
[tex]\[ 15 \cos 4x - \cos x = 0 \][/tex]
We need to find values of [tex]\( x \)[/tex] where this equation holds true. After analyzing the behavior of this equation over the given domain, we find:

Solutions: There are no values of [tex]\( x \)[/tex] that satisfy this equation in the given interval.

### Equation 3: [tex]\( 16 \sin 3x - \sin x = 0 \)[/tex]

The equation can be rewritten as:
[tex]\[ 16 \sin 3x - \sin x = 0 \][/tex]
We need to find values of [tex]\( x \)[/tex] where this equation holds true. After analyzing the behavior of this equation over the given domain, we find:

Solutions: [tex]\( x = 0^\circ \)[/tex], [tex]\( x = 180^\circ \)[/tex], and [tex]\( x = 360^\circ \)[/tex]

### Equation 4: [tex]\( 18 \sin (x + 10^\circ) + \sin x = 0 \)[/tex]

The equation can be rewritten as:
[tex]\[ 18 \sin (x + 10^\circ) + \sin x = 0 \][/tex]
We need to find values of [tex]\( x \)[/tex] where this equation holds true. After analyzing the behavior of this equation over the given domain, we find:

Solutions: There are no values of [tex]\( x \)[/tex] that satisfy this equation in the given interval.

### Equation 5: [tex]\( 19 \cos (2x + 10^\circ) + \cos (2x - 10^\circ) = 0 \)[/tex]

The equation can be rewritten as:
[tex]\[ 19 \cos (2x + 10^\circ) + \cos (2x - 10^\circ) = 0 \][/tex]
We need to find values of [tex]\( x \)[/tex] where this equation holds true. After analyzing the behavior of this equation over the given domain, we find:

Solutions: There are no values of [tex]\( x \)[/tex] that satisfy this equation in the given interval.

### Equation 6: [tex]\( 20 \cos (x + 20^\circ) - \cos (x - 70^\circ) = 0 \)[/tex]

The equation can be rewritten as:
[tex]\[ 20 \cos (x + 20^\circ) - \cos (x - 70^\circ) = 0 \][/tex]
We need to find values of [tex]\( x \)[/tex] where this equation holds true. After analyzing the behavior of this equation over the given domain, we find:

Solutions: There are no values of [tex]\( x \)[/tex] that satisfy this equation in the given interval.

### Summary of Solutions:
1. [tex]\( 14 \cos x + \cos 5x = 0 \)[/tex]
- [tex]\( x = 90^\circ \)[/tex]
- [tex]\( x = 270^\circ \)[/tex]
2. [tex]\( 15 \cos 4x - \cos x = 0 \)[/tex]
- No solutions.
3. [tex]\( 16 \sin 3x - \sin x = 0 \)[/tex]
- [tex]\( x = 0^\circ \)[/tex]
- [tex]\( x = 180^\circ \)[/tex]
- [tex]\( x = 360^\circ \)[/tex]
4. [tex]\( 18 \sin (x + 10^\circ) + \sin x = 0 \)[/tex]
- No solutions.
5. [tex]\( 19 \cos (2x + 10^\circ) + \cos (2x - 10^\circ) = 0 \)[/tex]
- No solutions.
6. [tex]\( 20 \cos (x + 20^\circ) - \cos (x - 70^\circ) = 0 \)[/tex]
- No solutions.

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