Trigonometry Examples

$7 \sin^{2} (x) - \sin (x) = 0$

Step 1

Factor the left side of the equation.

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Step 1.1

Let $u = \sin (x)$ . Substitute $u$ for all occurrences of $\sin (x)$ .

$7 u^{2} - u = 0$

Step 1.2

Factor $u$ out of $7 u^{2} - u$ .

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Step 1.2.1

Factor $u$ out of $7 u^{2}$ .

$u (7 u) - u = 0$

Step 1.2.2

Factor $u$ out of $- u$ .

$u (7 u) + u \cdot - 1 = 0$

Step 1.2.3

Factor $u$ out of $u (7 u) + u \cdot - 1$ .

$u (7 u - 1) = 0$

Step 1.3

Replace all occurrences of $u$ with $\sin (x)$ .

$\sin (x) (7 \sin (x) - 1) = 0$

Step 2

If any individual factor on the left side of the equation is equal to $0$ , the entire expression will be equal to $0$ .

$\sin (x) = 0$

$7 \sin (x) - 1 = 0$

Step 3

Set $\sin (x)$ equal to $0$ and solve for $x$ .

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Step 3.1

Set $\sin (x)$ equal to $0$ .

$\sin (x) = 0$

Step 3.2

Solve $\sin (x) = 0$ for $x$ .

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Step 3.2.1

Take the inverse sine of both sides of the equation to extract $x$ from inside the sine.

$x = \arcsin (0)$

Step 3.2.2

Simplify the right side.

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Step 3.2.2.1

The exact value of $\arcsin (0)$ is $0$ .

$x = 0$

Step 3.2.3

The sine function is positive in the first and second quadrants. To find the second solution, subtract the reference angle from $π$ to find the solution in the second quadrant.

$x = π - 0$

Step 3.2.4

Subtract $0$ from $π$ .

$x = π$

Step 3.2.5

Find the period of $\sin (x)$ .

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Step 3.2.5.1

The period of the function can be calculated using $\frac{2 π}{| b |}$ .

$\frac{2 π}{| b |}$

Step 3.2.5.2

Replace $b$ with $1$ in the formula for period.

$\frac{2 π}{| 1 |}$

Step 3.2.5.3

The absolute value is the distance between a number and zero. The distance between $0$ and $1$ is $1$ .

$\frac{2 π}{1}$

Step 3.2.5.4

Divide $2 π$ by $1$ .

$2 π$

Step 3.2.6

The period of the $\sin (x)$ function is $2 π$ so values will repeat every $2 π$ radians in both directions.

$x = 2 π n, π + 2 π n$ , for any integer $n$

Step 4

Set $7 \sin (x) - 1$ equal to $0$ and solve for $x$ .

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Step 4.1

Set $7 \sin (x) - 1$ equal to $0$ .

$7 \sin (x) - 1 = 0$

Step 4.2

Solve $7 \sin (x) - 1 = 0$ for $x$ .

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Step 4.2.1

Add $1$ to both sides of the equation.

$7 \sin (x) = 1$

Step 4.2.2

Divide each term in $7 \sin (x) = 1$ by $7$ and simplify.

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Step 4.2.2.1

Divide each term in $7 \sin (x) = 1$ by $7$ .

$\frac{7 \sin (x)}{7} = \frac{1}{7}$

Step 4.2.2.2

Simplify the left side.

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Step 4.2.2.2.1

Cancel the common factor of $7$ .

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Step 4.2.2.2.1.1

Cancel the common factor.

$\frac{7 \sin (x)}{7} = \frac{1}{7}$

Step 4.2.2.2.1.2

Divide $\sin (x)$ by $1$ .

$\sin (x) = \frac{1}{7}$

Step 4.2.3

Take the inverse sine of both sides of the equation to extract $x$ from inside the sine.

$x = \arcsin (\frac{1}{7})$

Step 4.2.4

Simplify the right side.

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Step 4.2.4.1

Evaluate $\arcsin (\frac{1}{7})$ .

$x = 0.14334756$

Step 4.2.5

The sine function is positive in the first and second quadrants. To find the second solution, subtract the reference angle from $π$ to find the solution in the second quadrant.

$x = (3.14159265) - 0.14334756$

Step 4.2.6

Solve for $x$ .

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Step 4.2.6.1

Remove parentheses.

$x = 3.14159265 - 0.14334756$

Step 4.2.6.2

Remove parentheses.

$x = (3.14159265) - 0.14334756$

Step 4.2.6.3

Subtract $0.14334756$ from $3.14159265$ .

$x = 2.99824508$

Step 4.2.7

Find the period of $\sin (x)$ .

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Step 4.2.7.1

The period of the function can be calculated using $\frac{2 π}{| b |}$ .

$\frac{2 π}{| b |}$

Step 4.2.7.2

Replace $b$ with $1$ in the formula for period.

$\frac{2 π}{| 1 |}$

Step 4.2.7.3

The absolute value is the distance between a number and zero. The distance between $0$ and $1$ is $1$ .

$\frac{2 π}{1}$

Step 4.2.7.4

Divide $2 π$ by $1$ .

$2 π$

Step 4.2.8

The period of the $\sin (x)$ function is $2 π$ so values will repeat every $2 π$ radians in both directions.

$x = 0.14334756 + 2 π n, 2.99824508 + 2 π n$ , for any integer $n$

Step 5

The final solution is all the values that make $\sin (x) (7 \sin (x) - 1) = 0$ true.

$x = 2 π n, π + 2 π n, 0.14334756 + 2 π n, 2.99824508 + 2 π n$ , for any integer $n$

Step 6

Consolidate $2 π n$ and $π + 2 π n$ to $π n$ .

$x = π n, 0.14334756 + 2 π n, 2.99824508 + 2 π n$ , for any integer $n$