Q1. - Algebra 2

Question

Identify the vertical shift, amplitude, period and phase shift of the graph of $y=3\cos \left(2x-90°\right)+15$ and then graph the function.

Step-by-Step Solution

Answer

The vertical shift of $y=3\cos \left(2x-90°\right)+15$ is $15$.

The amplitude of $y=3\cos \left(2x-90°\right)+15$ is $3$.

The period of $y=3\cos \left(2x-90°\right)+15$ is $\pi$.

The phase shift of $y=3\cos \left(2x-90°\right)+15$ is $45°$.

Step 1. Write down the given information.

The given function is $y=3\cos \left(2x-90°\right)+15$.

Step 2. Concept used.

A function of the form:

$y=a\sin b\left(\theta -h\right)+k,y=a\cos b\left(\theta -h\right)+k \text{and }y=a\cos \left(bx\right)y=a\tan b\left(\theta -h\right)+k$

has amplitude of $\left|a\right|$, vertical shift $\left(k\right)$ and period $\frac{360°}{\left|b\right|} \text{or }\frac{2\pi }{\left|b\right|}$ for sine and cosine functions and a period of $\frac{180°}{\left|b\right|} \text{or }\frac{\pi }{\left|b\right|}$ for tangent function. The phase shift for the functions is $\left(h\right)$.

Step 3. Evaluating vertical shift, amplitude, period and phase shift of the given function.

With the help of concept stated above, the vertical shift, amplitude, period and phase shift of the function is evaluated as:

Re-write the given function as $y=3\cos \left[2\left(x-45°\right)\right]+15$.

The vertical shift of the function $y=3\cos \left[2\left(x-45°\right)\right]+15$ is $15$ and a positive vertical shift of indicates that the vertical shift is upwards.

The amplitude of $y=3\cos \left[2\left(x-45°\right)\right]+15$ is $\left|3\right|=3$.

The period of $y=3\cos \left[2\left(x-45°\right)\right]+15$ is $\frac{2\pi }{\left|2\right|}=\pi$.

The phase shift of $y=3\cos \left[2\left(x-45°\right)\right]+15$ is $45°$ and a positive value of phase shift indicates that the phase shift is to the right.

Step 4. Conclusion.

The vertical shift of $y=3\cos \left[2\left(x-45°\right)\right]+15$ is $15$.

The amplitude of $y=3\cos \left[2\left(x-45°\right)\right]+15$ is $3$.

The period of $y=3\cos \left[2\left(x-45°\right)\right]+15$ is $\pi$.

The phase shift of $y=3\cos \left[2\left(x-45°\right)\right]+15$ is $45°$.