Trigonometry Examples

r = 14 cos (x)

$r = 14 \cos (x)$

Step 1

Use the form

a cos (b x - c) + d

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

a = 14

$a = 14$

b = 1

$b = 1$

c = 0

$c = 0$

d = 0

$d = 0$

Step 2

Find the amplitude

| a |

$| a |$ .

Amplitude:

14

$14$

Step 3

Find the period of

14 cos (x)

$14 \cos (x)$ .

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Step 3.1

The period of the function can be calculated using

\frac{2 π}{| b |}

$\frac{2 π}{| b |}$ .

\frac{2 π}{| b |}

$\frac{2 π}{| b |}$

Step 3.2

Replace

b

$b$ with

1

$1$ in the formula for period.

\frac{2 π}{| 1 |}

$\frac{2 π}{| 1 |}$

Step 3.3

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

0

$0$ and

1

$1$ is

1

$1$ .

\frac{2 π}{1}

$\frac{2 π}{1}$

Step 3.4

Divide

2 π

$2 π$ by

1

$1$ .

2 π

$2 π$

2 π

$2 π$

Step 4

Find the phase shift using the formula

\frac{c}{b}

$\frac{c}{b}$ .

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Step 4.1

The phase shift of the function can be calculated from

\frac{c}{b}

$\frac{c}{b}$ .

Phase Shift:

\frac{c}{b}

$\frac{c}{b}$

Step 4.2

Replace the values of

c

$c$ and

b

$b$ in the equation for phase shift.

Phase Shift:

\frac{0}{1}

$\frac{0}{1}$

Step 4.3

Divide

0

$0$ by

1

$1$ .

Phase Shift:

0

$0$

Phase Shift:

0

$0$

Step 5

List the properties of the trigonometric function.

Amplitude:

14

$14$

Period:

2 π

$2 π$

Phase Shift: None

Vertical Shift: None

Step 6

Select a few points to graph.

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Step 6.1

Find the point at

x = 0

$x = 0$ .

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Step 6.1.1

Replace the variable

x

$x$ with

0

$0$ in the expression.

f (0) = 14 cos (0)

$f (0) = 14 \cos (0)$

Step 6.1.2

Simplify the result.

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Step 6.1.2.1

The exact value of

cos (0)

$\cos (0)$ is

1

$1$ .

f (0) = 14 \cdot 1

$f (0) = 14 \cdot 1$

Step 6.1.2.2

Multiply

14

$14$ by

1

$1$ .

f (0) = 14

$f (0) = 14$

Step 6.1.2.3

The final answer is

14

$14$ .

14

$14$

14

$14$

14

$14$

Step 6.2

Find the point at

x = \frac{π}{2}

$x = \frac{π}{2}$ .

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Step 6.2.1

Replace the variable

x

$x$ with

\frac{π}{2}

$\frac{π}{2}$ in the expression.

f (\frac{π}{2}) = 14 cos (\frac{π}{2})

$f (\frac{π}{2}) = 14 \cos (\frac{π}{2})$

Step 6.2.2

Simplify the result.

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Step 6.2.2.1

The exact value of

cos (\frac{π}{2})

$\cos (\frac{π}{2})$ is

0

$0$ .

f (\frac{π}{2}) = 14 \cdot 0

$f (\frac{π}{2}) = 14 \cdot 0$

Step 6.2.2.2

Multiply

14

$14$ by

0

$0$ .

f (\frac{π}{2}) = 0

$f (\frac{π}{2}) = 0$

Step 6.2.2.3

The final answer is

0

$0$ .

0

$0$

0

$0$

0

$0$

Step 6.3

Find the point at

x = π

$x = π$ .

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Step 6.3.1

Replace the variable

x

$x$ with

π

$π$ in the expression.

f (π) = 14 cos (π)

$f (π) = 14 \cos (π)$

Step 6.3.2

Simplify the result.

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Step 6.3.2.1

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

f (π) = 14 (- cos (0))

$f (π) = 14 (- \cos (0))$

Step 6.3.2.2

The exact value of

cos (0)

$\cos (0)$ is

1

$1$ .

f (π) = 14 (- 1 \cdot 1)

$f (π) = 14 (- 1 \cdot 1)$

Step 6.3.2.3

Multiply

14 (- 1 \cdot 1)

$14 (- 1 \cdot 1)$ .

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Step 6.3.2.3.1

Multiply

- 1

$- 1$ by

1

$1$ .

f (π) = 14 \cdot - 1

$f (π) = 14 \cdot - 1$

Step 6.3.2.3.2

Multiply

14

$14$ by

- 1

$- 1$ .

f (π) = - 14

$f (π) = - 14$

f (π) = - 14

$f (π) = - 14$

Step 6.3.2.4

The final answer is

- 14

$- 14$ .

- 14

$- 14$

- 14

$- 14$

- 14

$- 14$

Step 6.4

Find the point at

x = \frac{3 π}{2}

$x = \frac{3 π}{2}$ .

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Step 6.4.1

Replace the variable

x

$x$ with

\frac{3 π}{2}

$\frac{3 π}{2}$ in the expression.

f (\frac{3 π}{2}) = 14 cos (\frac{3 π}{2})

$f (\frac{3 π}{2}) = 14 \cos (\frac{3 π}{2})$

Step 6.4.2

Simplify the result.

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Step 6.4.2.1

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

f (\frac{3 π}{2}) = 14 cos (\frac{π}{2})

$f (\frac{3 π}{2}) = 14 \cos (\frac{π}{2})$

Step 6.4.2.2

The exact value of

cos (\frac{π}{2})

$\cos (\frac{π}{2})$ is

0

$0$ .

f (\frac{3 π}{2}) = 14 \cdot 0

$f (\frac{3 π}{2}) = 14 \cdot 0$

Step 6.4.2.3

Multiply

14

$14$ by

0

$0$ .

f (\frac{3 π}{2}) = 0

$f (\frac{3 π}{2}) = 0$

Step 6.4.2.4

The final answer is

0

$0$ .

0

$0$

0

$0$

0

$0$

Step 6.5

Find the point at

x = 2 π

$x = 2 π$ .

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Step 6.5.1

Replace the variable

x

$x$ with

2 π

$2 π$ in the expression.

f (2 π) = 14 cos (2 π)

$f (2 π) = 14 \cos (2 π)$

Step 6.5.2

Simplify the result.

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Step 6.5.2.1

Subtract full rotations of

2 π

$2 π$ until the angle is greater than or equal to

0

$0$ and less than

2 π

$2 π$ .

f (2 π) = 14 cos (0)

$f (2 π) = 14 \cos (0)$

Step 6.5.2.2

The exact value of

cos (0)

$\cos (0)$ is

1

$1$ .

f (2 π) = 14 \cdot 1

$f (2 π) = 14 \cdot 1$

Step 6.5.2.3

Multiply

14

$14$ by

1

$1$ .

f (2 π) = 14

$f (2 π) = 14$

Step 6.5.2.4

The final answer is

14

$14$ .

14

$14$

14

$14$

14

$14$

Step 6.6

List the points in a table.

\begin{matrix} x & f (x) 0 & 14 \frac{π}{2} & 0 π & - 14 \frac{3 π}{2} & 0 2 π & 14 \end{matrix}

$\begin{array}{c} x & f (x) \\ 0 & 14 \\ \frac{π}{2} & 0 \\ π & - 14 \\ \frac{3 π}{2} & 0 \\ 2 π & 14 \end{array}$

\begin{matrix} x & f (x) 0 & 14 \frac{π}{2} & 0 π & - 14 \frac{3 π}{2} & 0 2 π & 14 \end{matrix}

$\begin{array}{c} x & f (x) \\ 0 & 14 \\ \frac{π}{2} & 0 \\ π & - 14 \\ \frac{3 π}{2} & 0 \\ 2 π & 14 \end{array}$

Step 7

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

Amplitude:

14

$14$

Period:

2 π

$2 π$

Phase Shift: None

Vertical Shift: None

\begin{matrix} x & f (x) 0 & 14 \frac{π}{2} & 0 π & - 14 \frac{3 π}{2} & 0 2 π & 14 \end{matrix}

$\begin{array}{c} x & f (x) \\ 0 & 14 \\ \frac{π}{2} & 0 \\ π & - 14 \\ \frac{3 π}{2} & 0 \\ 2 π & 14 \end{array}$

Step 8