Trigonometry Examples

$f (x) = 5 \sin (\frac{1}{3} x - \frac{π}{3})$

Step 1

Use the form $a \sin (b x - c) + d$ to find the variables used to find the amplitude, period, phase shift, and vertical shift.

$a = 5$

$b = \frac{1}{3}$

$c = \frac{π}{3}$

$d = 0$

Step 2

Find the amplitude $| a |$ .

Amplitude: $5$

Step 3

Find the period of $5 \sin (\frac{x}{3} - \frac{π}{3})$ .

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Step 3.1

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

$\frac{2 π}{| b |}$

Step 3.2

Replace $b$ with $\frac{1}{3}$ in the formula for period.

$\frac{2 π}{| \frac{1}{3} |}$

Step 3.3

$\frac{1}{3}$ is approximately $0.\overline{3}$ which is positive so remove the absolute value

$\frac{2 π}{\frac{1}{3}}$

Step 3.4

Multiply the numerator by the reciprocal of the denominator.

$2 π \cdot 3$

Step 3.5

Multiply $3$ by $2$ .

$6 π$

Step 4

Find the phase shift using the formula $\frac{c}{b}$ .

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Step 4.1

The phase shift of the function can be calculated from $\frac{c}{b}$ .

Phase Shift: $\frac{c}{b}$

Step 4.2

Replace the values of $c$ and $b$ in the equation for phase shift.

Phase Shift: $\frac{\frac{π}{3}}{\frac{1}{3}}$

Step 4.3

Multiply the numerator by the reciprocal of the denominator.

Phase Shift: $\frac{π}{3} \cdot 3$

Step 4.4

Cancel the common factor of $3$ .

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Step 4.4.1

Cancel the common factor.

Phase Shift: $\frac{π}{3} \cdot 3$

Step 4.4.2

Rewrite the expression.

Phase Shift: $π$

Step 5

List the properties of the trigonometric function.

Amplitude: $5$

Period: $6 π$

Phase Shift: $π$ ( $π$ to the right)

Vertical Shift: None

Step 6

Select a few points to graph.

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Step 6.1

Find the point at $x = π$ .

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Step 6.1.1

Replace the variable $x$ with $π$ in the expression.

$f (π) = 5 \sin (\frac{π}{3} - \frac{π}{3})$

Step 6.1.2

Simplify the result.

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Step 6.1.2.1

Combine the numerators over the common denominator.

$f (π) = 5 \sin (\frac{π - π}{3})$

Step 6.1.2.2

Subtract $π$ from $π$ .

$f (π) = 5 \sin (\frac{0}{3})$

Step 6.1.2.3

Divide $0$ by $3$ .

$f (π) = 5 \sin (0)$

Step 6.1.2.4

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

$f (π) = 5 \cdot 0$

Step 6.1.2.5

Multiply $5$ by $0$ .

$f (π) = 0$

Step 6.1.2.6

The final answer is $0$ .

$0$

Step 6.2

Find the point at $x = \frac{5 π}{2}$ .

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Step 6.2.1

Replace the variable $x$ with $\frac{5 π}{2}$ in the expression.

$f (\frac{5 π}{2}) = 5 \sin (\frac{\frac{5 π}{2}}{3} - \frac{π}{3})$

Step 6.2.2

Simplify the result.

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Step 6.2.2.1

Combine the numerators over the common denominator.

$f (\frac{5 π}{2}) = 5 \sin (\frac{\frac{5 π}{2} - π}{3})$

Step 6.2.2.2

To write $- π$ as a fraction with a common denominator, multiply by $\frac{2}{2}$ .

$f (\frac{5 π}{2}) = 5 \sin (\frac{\frac{5 π}{2} - π \cdot \frac{2}{2}}{3})$

Step 6.2.2.3

Combine fractions.

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Step 6.2.2.3.1

Combine $- π$ and $\frac{2}{2}$ .

$f (\frac{5 π}{2}) = 5 \sin (\frac{\frac{5 π}{2} + \frac{- π \cdot 2}{2}}{3})$

Step 6.2.2.3.2

Combine the numerators over the common denominator.

$f (\frac{5 π}{2}) = 5 \sin (\frac{\frac{5 π - π \cdot 2}{2}}{3})$

Step 6.2.2.4

Simplify the numerator.

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Step 6.2.2.4.1

Multiply $2$ by $- 1$ .

$f (\frac{5 π}{2}) = 5 \sin (\frac{\frac{5 π - 2 π}{2}}{3})$

Step 6.2.2.4.2

Subtract $2 π$ from $5 π$ .

$f (\frac{5 π}{2}) = 5 \sin (\frac{\frac{3 π}{2}}{3})$

Step 6.2.2.5

Multiply the numerator by the reciprocal of the denominator.

$f (\frac{5 π}{2}) = 5 \sin (\frac{3 π}{2} \cdot \frac{1}{3})$

Step 6.2.2.6

Cancel the common factor of $3$ .

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Step 6.2.2.6.1

Factor $3$ out of $3 π$ .

$f (\frac{5 π}{2}) = 5 \sin (\frac{3 (π)}{2} \cdot \frac{1}{3})$

Step 6.2.2.6.2

Cancel the common factor.

$f (\frac{5 π}{2}) = 5 \sin (\frac{3 π}{2} \cdot \frac{1}{3})$

Step 6.2.2.6.3

Rewrite the expression.

$f (\frac{5 π}{2}) = 5 \sin (\frac{π}{2})$

Step 6.2.2.7

The exact value of $\sin (\frac{π}{2})$ is $1$ .

$f (\frac{5 π}{2}) = 5 \cdot 1$

Step 6.2.2.8

Multiply $5$ by $1$ .

$f (\frac{5 π}{2}) = 5$

Step 6.2.2.9

The final answer is $5$ .

$5$

Step 6.3

Find the point at $x = 4 π$ .

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Step 6.3.1

Replace the variable $x$ with $4 π$ in the expression.

$f (4 π) = 5 \sin (\frac{4 π}{3} - \frac{π}{3})$

Step 6.3.2

Simplify the result.

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Step 6.3.2.1

Combine the numerators over the common denominator.

$f (4 π) = 5 \sin (\frac{4 π - π}{3})$

Step 6.3.2.2

Subtract $π$ from $4 π$ .

$f (4 π) = 5 \sin (\frac{3 π}{3})$

Step 6.3.2.3

Cancel the common factor of $3$ .

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Step 6.3.2.3.1

Cancel the common factor.

$f (4 π) = 5 \sin (\frac{3 π}{3})$

Step 6.3.2.3.2

Divide $π$ by $1$ .

$f (4 π) = 5 \sin (π)$

Step 6.3.2.4

Apply the reference angle by finding the angle with equivalent trig values in the first quadrant.

$f (4 π) = 5 \sin (0)$

Step 6.3.2.5

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

$f (4 π) = 5 \cdot 0$

Step 6.3.2.6

Multiply $5$ by $0$ .

$f (4 π) = 0$

Step 6.3.2.7

The final answer is $0$ .

$0$

Step 6.4

Find the point at $x = \frac{11 π}{2}$ .

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Step 6.4.1

Replace the variable $x$ with $\frac{11 π}{2}$ in the expression.

$f (\frac{11 π}{2}) = 5 \sin (\frac{\frac{11 π}{2}}{3} - \frac{π}{3})$

Step 6.4.2

Simplify the result.

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Step 6.4.2.1

Combine the numerators over the common denominator.

$f (\frac{11 π}{2}) = 5 \sin (\frac{\frac{11 π}{2} - π}{3})$

Step 6.4.2.2

To write $- π$ as a fraction with a common denominator, multiply by $\frac{2}{2}$ .

$f (\frac{11 π}{2}) = 5 \sin (\frac{\frac{11 π}{2} - π \cdot \frac{2}{2}}{3})$

Step 6.4.2.3

Combine fractions.

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Step 6.4.2.3.1

Combine $- π$ and $\frac{2}{2}$ .

$f (\frac{11 π}{2}) = 5 \sin (\frac{\frac{11 π}{2} + \frac{- π \cdot 2}{2}}{3})$

Step 6.4.2.3.2

Combine the numerators over the common denominator.

$f (\frac{11 π}{2}) = 5 \sin (\frac{\frac{11 π - π \cdot 2}{2}}{3})$

Step 6.4.2.4

Simplify the numerator.

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Step 6.4.2.4.1

Multiply $2$ by $- 1$ .

$f (\frac{11 π}{2}) = 5 \sin (\frac{\frac{11 π - 2 π}{2}}{3})$

Step 6.4.2.4.2

Subtract $2 π$ from $11 π$ .

$f (\frac{11 π}{2}) = 5 \sin (\frac{\frac{9 π}{2}}{3})$

Step 6.4.2.5

Multiply the numerator by the reciprocal of the denominator.

$f (\frac{11 π}{2}) = 5 \sin (\frac{9 π}{2} \cdot \frac{1}{3})$

Step 6.4.2.6

Cancel the common factor of $3$ .

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Step 6.4.2.6.1

Factor $3$ out of $9 π$ .

$f (\frac{11 π}{2}) = 5 \sin (\frac{3 (3 π)}{2} \cdot \frac{1}{3})$

Step 6.4.2.6.2

Cancel the common factor.

$f (\frac{11 π}{2}) = 5 \sin (\frac{3 (3 π)}{2} \cdot \frac{1}{3})$

Step 6.4.2.6.3

Rewrite the expression.

$f (\frac{11 π}{2}) = 5 \sin (\frac{3 π}{2})$

Step 6.4.2.7

Apply the reference angle by finding the angle with equivalent trig values in the first quadrant. Make the expression negative because sine is negative in the fourth quadrant.

$f (\frac{11 π}{2}) = 5 (- \sin (\frac{π}{2}))$

Step 6.4.2.8

The exact value of $\sin (\frac{π}{2})$ is $1$ .

$f (\frac{11 π}{2}) = 5 (- 1 \cdot 1)$

Step 6.4.2.9

Multiply $5 (- 1 \cdot 1)$ .

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Step 6.4.2.9.1

Multiply $- 1$ by $1$ .

$f (\frac{11 π}{2}) = 5 \cdot - 1$

Step 6.4.2.9.2

Multiply $5$ by $- 1$ .

$f (\frac{11 π}{2}) = - 5$

Step 6.4.2.10

The final answer is $- 5$ .

$- 5$

Step 6.5

Find the point at $x = 7 π$ .

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Step 6.5.1

Replace the variable $x$ with $7 π$ in the expression.

$f (7 π) = 5 \sin (\frac{7 π}{3} - \frac{π}{3})$

Step 6.5.2

Simplify the result.

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Step 6.5.2.1

Combine the numerators over the common denominator.

$f (7 π) = 5 \sin (\frac{7 π - π}{3})$

Step 6.5.2.2

Subtract $π$ from $7 π$ .

$f (7 π) = 5 \sin (\frac{6 π}{3})$

Step 6.5.2.3

Cancel the common factor of $6$ and $3$ .

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Step 6.5.2.3.1

Factor $3$ out of $6 π$ .

$f (7 π) = 5 \sin (\frac{3 (2 π)}{3})$

Step 6.5.2.3.2

Cancel the common factors.

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Step 6.5.2.3.2.1

Factor $3$ out of $3$ .

$f (7 π) = 5 \sin (\frac{3 (2 π)}{3 (1)})$

Step 6.5.2.3.2.2

Cancel the common factor.

$f (7 π) = 5 \sin (\frac{3 (2 π)}{3 \cdot 1})$

Step 6.5.2.3.2.3

Rewrite the expression.

$f (7 π) = 5 \sin (\frac{2 π}{1})$

Step 6.5.2.3.2.4

Divide $2 π$ by $1$ .

$f (7 π) = 5 \sin (2 π)$

Step 6.5.2.4

Subtract full rotations of $2 π$ until the angle is greater than or equal to $0$ and less than $2 π$ .

$f (7 π) = 5 \sin (0)$

Step 6.5.2.5

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

$f (7 π) = 5 \cdot 0$

Step 6.5.2.6

Multiply $5$ by $0$ .

$f (7 π) = 0$

Step 6.5.2.7

The final answer is $0$ .

$0$

Step 6.6

List the points in a table.

$\begin{array}{c} x & f (x) \\ π & 0 \\ \frac{5 π}{2} & 5 \\ 4 π & 0 \\ \frac{11 π}{2} & - 5 \\ 7 π & 0 \end{array}$

Step 7

The trig function can be graphed using the amplitude, period, phase shift, vertical shift, and the points.

Amplitude: $5$

Period: $6 π$

Phase Shift: $π$ ( $π$ to the right)

Vertical Shift: None

$\begin{array}{c} x & f (x) \\ π & 0 \\ \frac{5 π}{2} & 5 \\ 4 π & 0 \\ \frac{11 π}{2} & - 5 \\ 7 π & 0 \end{array}$

Step 8