The calculation is incorrect, because the slope is defined as

So, Emma has inverted numerator and denominator: she has calculated the inverse of the slope.
The correct calculation would be

ANSWER

EXPLANATION
The given function is,

This function has a period of

just as the parent function

A sample period of this parent function is
![[ 0 , 2\pi]](https://tex.z-dn.net/?f=%5B%200%20%2C%202%5Cpi%5D)
Which begins at zero.
For the transformed function,

There has been a horizontal shift of

to the left.
The transformed function will have a sample period,
![[ - \frac{\pi}{4} , \frac{7\pi}{4} ]](https://tex.z-dn.net/?f=%5B%20-%20%5Cfrac%7B%5Cpi%7D%7B4%7D%20%2C%20%5Cfrac%7B7%5Cpi%7D%7B4%7D%20%5D)
Therefore a sample period begins at
See the attached picture:
We will see that the solution in the given interval is: x = 0.349 radians.
<h3>How to solve equations with the variable in the argument of a cosine?</h3>
We want to solve:
cos(3*x) = 1/2
Here we must use the inverse cosine function, Acos(x). Remember that:
cos(Acos(x)) = Acos(cos(x)) = x.
If we apply that in both sides, we get:
Acos( cos(3x) ) = Acos(1/2)
3*x = Acos(1/2)
x = Acos(1/2)/3 = 0.349
So x is equal to 0.349 radians, which belongs to the given interval.
If you want to learn more about trigonometry, you can read:
brainly.com/question/8120556
Linear fonction's equation : y = ax
So only in y = 2x
2 is the constant of <span>proportionality</span>