Trigonometry Examples

$y = \cos (- 3 π x)$

Step 1

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

$a = 1$

$b = - 3 π$

$c = 0$

$d = 0$

Step 2

Find the amplitude $| a |$ .

Amplitude: $1$

Step 3

Find the period of $\cos (- 3 π x)$ .

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Step 3.1

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

$\frac{2 π}{| b |}$

Step 3.2

Replace $b$ with $- 3 π$ in the formula for period.

$\frac{2 π}{| - 3 π |}$

Step 3.3

$- 3 π$ is approximately $- 9.42477796$ which is negative so negate $- 3 π$ and remove the absolute value

$\frac{2 π}{3 π}$

Step 3.4

Cancel the common factor of $π$ .

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Step 3.4.1

Cancel the common factor.

$\frac{2 π}{3 π}$

Step 3.4.2

Rewrite the expression.

$\frac{2}{3}$

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: $\frac{0}{- 3 π}$

Step 4.3

Cancel the common factor of $0$ and $- 3$ .

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Step 4.3.1

Factor $3$ out of $0$ .

Phase Shift: $\frac{3 (0)}{- 3 π}$

Step 4.3.2

Cancel the common factors.

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Step 4.3.2.1

Factor $3$ out of $- 3 π$ .

Phase Shift: $\frac{3 (0)}{3 (- π)}$

Step 4.3.2.2

Cancel the common factor.

Phase Shift: $\frac{3 \cdot 0}{3 (- π)}$

Step 4.3.2.3

Rewrite the expression.

Phase Shift: $\frac{0}{- π}$

Step 4.4

Divide $0$ by $- π$ .

Phase Shift: $0$

Step 5

List the properties of the trigonometric function.

Amplitude: $1$

Period: $\frac{2}{3}$

Phase Shift: None

Vertical Shift: None

Step 6