The area of a regular polygon is half the product of the apothem and the perimeter. Note that we are given the apothem but are missing the perimeter. Let's first find the perimeter and use it to find the area.
Finding the Perimeter
To find the perimeter, let's start by drawing the radii of the given polygon.
The radii divide the square into four congruent isosceles triangles. Since corresponding angles of congruent figures are congruent, the vertex angles of the isosceles triangles formed by the radii are congruent. Moreover, since a full turn measures 360^(∘), we can divide 360 by 4 to obtain their measures.
360/4=90^(∘)
The vertex angles of the isosceles triangles measure 90^(∘) each.
Next, recall that the apothem bisects the vertex angle of the isosceles triangle formed by the radii. As a result, 45^(∘)-45^(∘)-90^(∘) triangles are obtained. Let's consider one of them.
In this type of special triangle, the legs are congruent and length of the hypotenuse is sqrt(2) times the length of a leg.
Other Leg: 5 in.
Not only does the apothem bisect the vertex angle of the right triangle but it also bisects its opposite side, which is a side of the square. Therefore, the length of one side of the given regular polygon is 2* 5= 10in.
In a square all four sides have the same length. Therefore, we can obtain its perimeter by multiplying the length of a side by 4.
Perimeter: 10* 4=40 in.
Finding the Area
Finally, we have that the apothem is 5in. and that the perimeter is 40 in. To find the area, we will substitute these two values in the formula A= 12ap and simplify.
