Big Ideas Math Geometry, 2014
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Big Ideas Math Geometry, 2014 View details
3. Areas of Polygons
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Exercise 26 Page 615

Remember that s represents the side length of a polygon.

See solution.

Practice makes perfect

We want to find the area of a regular hexagon given the apothem and the distance between the vertex and the center of a figure. Let's take a look at the given figure.

If we call the side length of the hexagon s, then the shorter leg of the drawn right triangle is 12 s.

Now, using the Pythagorean Theorem we can write the equation. According to this theorem the sum of the squared legs of a right triangle is equal to the squared hypotenuse. 13^2+(1/2 s)^2= 15^2 Let's solve the above equation. Notice that since s represents the side length, we will consider only the positive case when taking a square root of s^2.
13^2+(1/2s)^2=15^2
Simplify
13^2+(s/2)^2=15^2
13^2+s^2/2^2=15^2
169+s^2/4=225
s^2/4=56
s^2=224
Solve for s
sqrt(s^2)=sqrt(224)
s=sqrt(224)
s=14.9666...
s≈ 15
The side length is approximately 15, not 7.5. Next, let's recall the formula for the area of a regular polygon. A=1/2ans In this formula a is the apothem, n is the number of sides, and s is the side length of a regular polygon. To evaluate the area of the given figure let's substitute 13 for a, 6 for n, and 15 for s.
A=1/2ans
A=1/2( 13)(6)( 15)
A=1/2(1170)
A=1170/2
A=585
The area of the regular hexagon is approximately 585. Notice that this is only an approximation, as we used an approximate value to evaluate it.