Intermediate Geometry : How to find the length of the side of an equilateral triangle

Study concepts, example questions & explanations for Intermediate Geometry

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Example Questions

Example Question #211 : Triangles

An equilateral triangle is placed on top of a square as shown by the figure below.

5

Find the perimeter of the shape.

Possible Answers:

Correct answer:

Explanation:

Recall that the perimeter is the sum of all the exterior sides of a shape. The sides that add up to the perimeter are highlighted in red.

13

Since the equilateral triangle shares a side with the square, each of the five sides that are outlined have the same length.

Recall that the height of an equilateral triangle splits the triangle into  congruent  triangles.

We can then use the height to find the length of the side of the triangle.

Recall that a  triangle has sides that are in ratios of . The smallest side in the given figure is the base, the second longest side is the height, and the longest side is the side of the triangle itself.

Thus, we can use the ratio and the length of the height to set up the following equation:

Plug in the given height to find the length of the side.

Now, since the perimeter of the shape consists of  of these sides, we can use the following equation to find the perimeter.

Example Question #212 : Triangles

An equilateral triangle is placed on a square as shown by the figure below.

6

Find the perimeter of the shape.

Possible Answers:

Correct answer:

Explanation:

Recall that the perimeter is the sum of all the exterior sides of a shape. The sides that add up to the perimeter are highlighted in red.

13

Since the equilateral triangle shares a side with the square, each of the five sides that are outlined have the same length.

Recall that the height of an equilateral triangle splits the triangle into  congruent  triangles.

We can then use the height to find the length of the side of the triangle.

Recall that a  triangle has sides that are in ratios of . The smallest side in the given figure is the base, the second longest side is the height, and the longest side is the side of the triangle itself.

Thus, we can use the ratio and the length of the height to set up the following equation:

Plug in the given height to find the length of the side.

Now, since the perimeter of the shape consists of  of these sides, we can use the following equation to find the perimeter.

Example Question #213 : Triangles

An equilateral triangle is placed on a square as shown by the figure below.

7

Find the perimeter of the shape.

Possible Answers:

Correct answer:

Explanation:

Recall that the perimeter is the sum of all the exterior sides of a shape. The sides that add up to the perimeter are highlighted in red.

13

Since the equilateral triangle shares a side with the square, each of the five sides that are outlined have the same length.

Recall that the height of an equilateral triangle splits the triangle into  congruent  triangles.

We can then use the height to find the length of the side of the triangle.

Recall that a  triangle has sides that are in ratios of . The smallest side in the given figure is the base, the second longest side is the height, and the longest side is the side of the triangle itself.

Thus, we can use the ratio and the length of the height to set up the following equation:

Plug in the given height to find the length of the side.

Now, since the perimeter of the shape consists of  of these sides, we can use the following equation to find the perimeter.

Example Question #214 : Triangles

An equilateral triangle is placed on a square as shown by the figure below.

8

Find the perimeter of the shape.

Possible Answers:

Correct answer:

Explanation:

Recall that the perimeter is the sum of all the exterior sides of a shape. The sides that add up to the perimeter are highlighted in red.

13

Since the equilateral triangle shares a side with the square, each of the five sides that are outlined have the same length.

Recall that the height of an equilateral triangle splits the triangle into  congruent  triangles.

We can then use the height to find the length of the side of the triangle.

Recall that a  triangle has sides that are in ratios of . The smallest side in the given figure is the base, the second longest side is the height, and the longest side is the side of the triangle itself.

Thus, we can use the ratio and the length of the height to set up the following equation:

Plug in the given height to find the length of the side.

Now, since the perimeter of the shape consists of  of these sides, we can use the following equation to find the perimeter.

Example Question #215 : Triangles

An equilateral triangle is placed on a square as shown by the figure below.

9

Find the perimeter of the shape.

Possible Answers:

Correct answer:

Explanation:

Recall that the perimeter is the sum of all the exterior sides of a shape. The sides that add up to the perimeter are highlighted in red.

13

Since the equilateral triangle shares a side with the square, each of the five sides that are outlined have the same length.

Recall that the height of an equilateral triangle splits the triangle into  congruent  triangles.

We can then use the height to find the length of the side of the triangle.

Recall that a  triangle has sides that are in ratios of . The smallest side in the given figure is the base, the second longest side is the height, and the longest side is the side of the triangle itself.

Thus, we can use the ratio and the length of the height to set up the following equation:

Plug in the given height to find the length of the side.

Now, since the perimeter of the shape consists of  of these sides, we can use the following equation to find the perimeter.

Example Question #216 : Triangles

An equilateral triangle is placed on top of a square as shown by the figure below.

10

Find the perimeter of the shape.

Possible Answers:

Correct answer:

Explanation:

Recall that the perimeter is the sum of all the exterior sides of a shape. The sides that add up to the perimeter are highlighted in red.

13

Since the equilateral triangle shares a side with the square, each of the five sides that are outlined have the same length.

Recall that the height of an equilateral triangle splits the triangle into  congruent  triangles.

We can then use the height to find the length of the side of the triangle.

Recall that a  triangle has sides that are in ratios of . The smallest side in the given figure is the base, the second longest side is the height, and the longest side is the side of the triangle itself.

Thus, we can use the ratio and the length of the height to set up the following equation:

Plug in the given height to find the length of the side.

Now, since the perimeter of the shape consists of  of these sides, we can use the following equation to find the perimeter.

Example Question #217 : Triangles

An equilateral triangle is placed on a square as shown by the figure below.

11

Find the perimeter of the shape.

Possible Answers:

Correct answer:

Explanation:

Recall that the perimeter is the sum of all the exterior sides of a shape. The sides that add up to the perimeter are highlighted in red.

13

Since the equilateral triangle shares a side with the square, each of the five sides that are outlined have the same length.

Recall that the height of an equilateral triangle splits the triangle into  congruent  triangles.

We can then use the height to find the length of the side of the triangle.

Recall that a  triangle has sides that are in ratios of . The smallest side in the given figure is the base, the second longest side is the height, and the longest side is the side of the triangle itself.

Thus, we can use the ratio and the length of the height to set up the following equation:

Plug in the given height to find the length of the side.

Now, since the perimeter of the shape consists of  of these sides, we can use the following equation to find the perimeter.

Example Question #661 : Intermediate Geometry

An equilateral triangle is placed on top of a square as shown by the figure below.

12

Find the perimeter of the shape.

Possible Answers:

Correct answer:

Explanation:

Recall that the perimeter is the sum of all the exterior sides of a shape. The sides that add up to the perimeter are highlighted in red.

13

Since the equilateral triangle shares a side with the square, each of the five sides that are outlined have the same length.

Recall that the height of an equilateral triangle splits the triangle into  congruent  triangles.

We can then use the height to find the length of the side of the triangle.

Recall that a  triangle has sides that are in ratios of . The smallest side in the given figure is the base, the second longest side is the height, and the longest side is the side of the triangle itself.

Thus, we can use the ratio and the length of the height to set up the following equation:

Plug in the given height to find the length of the side.

Now, since the perimeter of the shape consists of  of these sides, we can use the following equation to find the perimeter.

Example Question #662 : Intermediate Geometry

Given: Regular Pentagon  with center . Construct segments  and  to form  .

True or false:  is an equilateral triangle.

Possible Answers:

False

True

Correct answer:

False

Explanation:

Below is regular Pentagon  with center , a segment drawn from  to each vertex - that is, each of its radii drawn.

Pentagon a

The measure of each angle of a regular pentagon can be calculated by setting  equal to 5 in the formula

and evaluating:

By symmetry, each radius bisects one of these angles. Specifically, 

.

An equilateral triangle has three angles of measure , so  is not equilateral.

Example Question #663 : Intermediate Geometry

Equilateral

Refer to the above diagram.  has perimeter 56.

True or false: 

Possible Answers:

False

True

Correct answer:

False

Explanation:

Assume . Then, since , it follows by the Isosceles Triangle Theorem that their opposite angles are also congruent. Since the measures of the angles of a triangle total , letting :

All three angles have measure , making  equiangular and, as a consequence, equilateral. Therefore, , and the perimeter, or the sum of the lengths of the sides, is

However, the perimeter is given to be 56. Therefore, .

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