Apothem of a Hexagon – Formulas and Examples

The apothem of a hexagon is the length of the line that joins the center of the hexagon with the center of one side. The apothem is the perpendicular line that connects the center of the hexagon with one side. The apothem can be very useful when we want to find the area of a hexagon since it allows us to use a simpler formula.

We can calculate the apothem by dividing the hexagon into six congruent triangles and using one of the triangles. Then, we use the Pythagorean theorem or trigonometry to derive different formulas.

GEOMETRY
formula for the apothem of a hexagon

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Learning about the apothem of a hexagon with examples.

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GEOMETRY
formula for the apothem of a hexagon

Relevant for

Learning about the apothem of a hexagon with examples.

See examples

Formula to find the apothem of a hexagon

There are two main methods that we can use to derive a formula for the apothem of a hexagon. Both methods involve dividing the hexagon into six congruent triangles as in the following image:

hexagon divided into six triangles

First method: We can use the Pythagorean theorem on one of the triangles formed. We know that the triangles formed are equilateral, so their three sides are equal. Also, drawing the apothem, we see that it divides the base into two equal parts as in the image:

hexagon divided into six triangles with apothem

Therefore, using these lengths, we have:

{{s}^2}={{a}^2}+{{(\frac{s}{2})}^2}

{{a}^2}={{s}^2}-{{(\frac{s}{2})}^2}

{{a}^2}={{s}^2}-\frac{{{s}^2}}{4}

{{a}^2}=\frac{3{{s}^2}}{4}

a=\frac{\sqrt{3}s}{2}

Second method: Similar to the previous method, we divide the hexagon into six congruent triangles. When plotting the apothem, we divide the triangle in half, which means that if we did this with all the triangles, we would have 12 small triangles in total.

To use trigonometry, we have to find the central angle. Since the total central angle equals 360°, the central angle of each small triangle measures 360 \div 12 = 30°:

hexagon divided into six triangles with apothem and internal angle

Now, we can use the tangent. We know that the tangent of an angle is equal to the opposite side over the adjacent side:

\tan(30°)=\frac{\text{opposite}}{\text{adjacent}}

\tan(30°)=\frac{\frac{s}{2}}{a}

\tan(30°)=\frac{s}{2a}

a=\frac{s}{2\tan(30°)}

Apothem of a hexagon – Examples with answers

The following examples use both formulas for the apothem of a hexagon seen above. Each example has its respective solution, but it is recommended that you try to solve the exercises yourself before looking at the result.

EXAMPLE 1

What is the length of the apothem of a hexagon that has sides of length 6 m?

First formula: Using the first formula with s = 6, we have:

a=\frac{\sqrt{3}s}{2}

a=\frac{\sqrt{3}(6)}{2}

a=5.2

The length of the apothem is 5.2 m.

Second formula: Using the second formula with s= 6, we have:

a=\frac{s}{2\tan(30°)}

a=\frac{6}{2\tan(30°)}

a=5.2

We see that we got the same result using both formulas.

EXAMPLE 2

A hexagon has sides of length 8 m. What is the length of its apothem?

First formula: We can use s = 8 in the first formula:

a=\frac{\sqrt{3}s}{2}

a=\frac{\sqrt{3}(8)}{2}

a=6.93

The length of the apothem is 6.93 m.

Second formula: If we now use the second formula with s = 8, we have:

a=\frac{s}{2\tan(30°)}

a=\frac{8}{2\tan(30°)}

a=6.93

We got the same length with both formulas.

EXAMPLE 3

What is the length of the apothem of a hexagon with sides of length 10 m?

First formula: Using the first formula with s = 10, we have:

a=\frac{\sqrt{3}s}{2}

a=\frac{\sqrt{3}(10)}{2}

a=8.66

The length of the apothem is 8.66 m.

Second formula: Using the second formula with s=10, we have:

a=\frac{s}{2\tan(30°)}

a=\frac{10}{2\tan(30°)}

a=8.66

The same result was obtained with both formulas.

EXAMPLE 4

What is the length of the sides of a hexagon that has an apothem of 7.5 m?

In this case, we have the length of the apothem and we want to find the length of the sides of the hexagon.

First formula: We use the first formula with a = 7.5 and solve for s:

a=\frac{\sqrt{3}s}{2}

7.5=\frac{\sqrt{3}s}{2}

15=\sqrt{3}s

s=8.66

The length of the sides of the hexagon is 8.66 m.

Second formula: We use the second formula with a = 7.5 and solve for s:

a=\frac{s}{2\tan(30°)}

7.5=\frac{s}{2\tan(30°)}

s=7.5(2\tan(30°))

s=8.66

We got the same length with both formulas.

EXAMPLE 5

What is the length of the sides of a hexagon that has an apothem of length 12 m?

Again, we use both formulas and solve for s.

First formula: We substitute a=12 and solve for s:

a=\frac{\sqrt{3}s}{2}

12=\frac{\sqrt{3}s}{2}

24=\sqrt{3}s

s=13.87

The length of the sides of the hexagon is 13.87 m.

Second formula: We substitute a=12 and we solve for s:

a=\frac{s}{2\tan(30°)}

12=\frac{s}{2\tan(30°)}

s=12(2\tan(30°))

s=13.86

In this case, we got a small difference in the decimals. This is due to the rounding used when performing the operations.


Apothem of a hexagon – Practice problems

Practice using the formulas of the hexagon apothem and solve the following problems. Select an answer and click “Check” to check your answer. If you need help with this, you can look at the solved examples above.

What is the length of the apothem of a hexagon that has sides of length 11m?

Choose an answer






A hexagon has sides of length 15m. What is the length of the apothem?

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A hexagon has an apothem of length 18m. What is the length of the sides?

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A hexagon has an apothem of length 20m. What is the length of the sides?

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