Answer:

Explanation:
To find the Apothem of a shape, we need to find how long the distance is from a vertex to the center of the shape.
We can see that they've already showed us how to do it: We need to find the length of the hypotenuse of the red triangle.
To do this, we can use the Pythagorean Theorem, which states that
.
We know that a is going to be half of 4, which is 2. We also know that b is going to be 4, so we can substitute inside the equation.

Hope this helped!