Precalculus Examples

$y = 4 \sin (\frac{1}{2} x)$

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.

$a = 4$

$b = \frac{1}{2}$

$c = 0$

$d = 0$

Step 2

Find the amplitude $| a |$ .

Amplitude: $4$

Step 3

Find the period of $4 \sin (\frac{x}{2})$ .

Tap for more steps...

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 $\frac{1}{2}$ in the formula for period.

$\frac{2 π}{| \frac{1}{2} |}$

Step 3.3

$\frac{1}{2}$ is approximately $0.5$ which is positive so remove the absolute value

$\frac{2 π}{\frac{1}{2}}$

Step 3.4

Multiply the numerator by the reciprocal of the denominator.

$2 π \cdot 2$

Step 3.5

Multiply $2$ by $2$ .

$4 π$

Step 4

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

Tap for more steps...

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: $\frac{0}{\frac{1}{2}}$

Step 4.3

Multiply the numerator by the reciprocal of the denominator.

Phase Shift: $0 \cdot 2$

Step 4.4

Multiply $0$ by $2$ .

Phase Shift: $0$

Step 5

List the properties of the trigonometric function.

Amplitude: $4$

Period: $4 π$

Phase Shift: None

Vertical Shift: None

Step 6

Select a few points to graph.

Tap for more steps...

Step 6.1

Find the point at $x = 0$ .

Tap for more steps...

Step 6.1.1

Replace the variable $x$ with $0$ in the expression.

$f (0) = 4 \sin (\frac{0}{2})$

Step 6.1.2

Simplify the result.

Tap for more steps...

Step 6.1.2.1

Divide $0$ by $2$ .

$f (0) = 4 \sin (0)$

Step 6.1.2.2

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

$f (0) = 4 \cdot 0$

Step 6.1.2.3

Multiply $4$ by $0$ .

$f (0) = 0$

Step 6.1.2.4

The final answer is $0$ .

$0$

Step 6.2

Find the point at $x = π$ .

Tap for more steps...

Step 6.2.1

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

$f (π) = 4 \sin (\frac{π}{2})$

Step 6.2.2

Simplify the result.

Tap for more steps...

Step 6.2.2.1

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

$f (π) = 4 \cdot 1$

Step 6.2.2.2

Multiply $4$ by $1$ .

$f (π) = 4$

Step 6.2.2.3

The final answer is $4$ .

$4$

Step 6.3

Find the point at $x = 2 π$ .

Tap for more steps...

Step 6.3.1

Replace the variable $x$ with $2 π$ in the expression.

$f (2 π) = 4 \sin (\frac{2 π}{2})$

Step 6.3.2

Simplify the result.

Tap for more steps...

Step 6.3.2.1

Cancel the common factor of $2$ .

Tap for more steps...

Step 6.3.2.1.1

Cancel the common factor.

$f (2 π) = 4 \sin (\frac{2 π}{2})$

Step 6.3.2.1.2

Divide $π$ by $1$ .

$f (2 π) = 4 \sin (π)$

Step 6.3.2.2

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

$f (2 π) = 4 \sin (0)$

Step 6.3.2.3

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

$f (2 π) = 4 \cdot 0$

Step 6.3.2.4

Multiply $4$ by $0$ .

$f (2 π) = 0$

Step 6.3.2.5

The final answer is $0$ .

$0$

Step 6.4

Find the point at $x = 3 π$ .

Tap for more steps...

Step 6.4.1

Replace the variable $x$ with $3 π$ in the expression.

$f (3 π) = 4 \sin (\frac{3 π}{2})$

Step 6.4.2

Simplify the result.

Tap for more steps...

Step 6.4.2.1

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.

$f (3 π) = 4 (- \sin (\frac{π}{2}))$

Step 6.4.2.2

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

$f (3 π) = 4 (- 1 \cdot 1)$

Step 6.4.2.3

Multiply $4 (- 1 \cdot 1)$ .

Tap for more steps...

Step 6.4.2.3.1

Multiply $- 1$ by $1$ .

$f (3 π) = 4 \cdot - 1$

Step 6.4.2.3.2

Multiply $4$ by $- 1$ .

$f (3 π) = - 4$

Step 6.4.2.4

The final answer is $- 4$ .

$- 4$

Step 6.5

Find the point at $x = 4 π$ .

Tap for more steps...

Step 6.5.1

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

$f (4 π) = 4 \sin (\frac{4 π}{2})$

Step 6.5.2

Simplify the result.

Tap for more steps...

Step 6.5.2.1

Cancel the common factor of $4$ and $2$ .

Tap for more steps...

Step 6.5.2.1.1

Factor $2$ out of $4 π$ .

$f (4 π) = 4 \sin (\frac{2 (2 π)}{2})$

Step 6.5.2.1.2

Cancel the common factors.

Tap for more steps...

Step 6.5.2.1.2.1

Factor $2$ out of $2$ .

$f (4 π) = 4 \sin (\frac{2 (2 π)}{2 (1)})$

Step 6.5.2.1.2.2

Cancel the common factor.

$f (4 π) = 4 \sin (\frac{2 (2 π)}{2 \cdot 1})$

Step 6.5.2.1.2.3

Rewrite the expression.

$f (4 π) = 4 \sin (\frac{2 π}{1})$

Step 6.5.2.1.2.4

Divide $2 π$ by $1$ .

$f (4 π) = 4 \sin (2 π)$

Step 6.5.2.2

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

$f (4 π) = 4 \sin (0)$

Step 6.5.2.3

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

$f (4 π) = 4 \cdot 0$

Step 6.5.2.4

Multiply $4$ by $0$ .

$f (4 π) = 0$

Step 6.5.2.5

The final answer is $0$ .

$0$

Step 6.6

List the points in a table.

$\begin{array}{c} x & f (x) \\ 0 & 0 \\ π & 4 \\ 2 π & 0 \\ 3 π & - 4 \\ 4 π & 0 \end{array}$

Step 7

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

Amplitude: $4$

Period: $4 π$

Phase Shift: None

Vertical Shift: None

$\begin{array}{c} x & f (x) \\ 0 & 0 \\ π & 4 \\ 2 π & 0 \\ 3 π & - 4 \\ 4 π & 0 \end{array}$

Step 8