In order to calculate the distance between the walls, let's use the tangent relation of angle 45° and the cosine relation of angle 60°.
The tangent is equal to the opposite leg over the adjacent leg, and the cosine is equal to the adjacent leg over the hypotenuse.
So we have:
[tex]\begin{gathered} \tan45°=\frac{40}{x}\\ \\ 1=\frac{40}{x}\\ \\ x=40\text{ m}\\ \\ \\ \\ \cos60°=\frac{y}{60}\\ \\ \frac{1}{2}=\frac{y}{60}\\ \\ 2y=60\\ \\ y=30\text{ m} \end{gathered}[/tex]
Now, adding the values of x and y (which are the distances from each wall to the laser source), we have the distance between the walls:
[tex]d=x+y=40+30=70\text{ m}[/tex]
Correct option: third one.
