Basic Geometry : 45/45/90 Right Isosceles Triangles

Study concepts, example questions & explanations for Basic Geometry

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Example Questions

Example Question #17 : How To Find The Length Of The Side Of A 45/45/90 Right Isosceles Triangle

If the hypotenuse of a right isosceles triangle is , what is the length of a side of the triangle?

Possible Answers:

Correct answer:

Explanation:

A right isosceles triangle is also a  triangle.

13

To find the length of a side, we will need to use the Pythagorean Theorem:

Since this is an isosceles triangle, 

The Pythagorean Theorem can then be rewritten as the following:

Since we are trying to find the length of a side of this triangle, solve for .

Simplify.

Multiply the fraction by one in the form of .

Solve.

Now, substitute in the length of the hypotenuse in for  to solve for the side of the triangle in the question.

Simplify.

Example Question #18 : How To Find The Length Of The Side Of A 45/45/90 Right Isosceles Triangle

In the figure, a right isosceles triangle is placed in a rectangle. What is the area of the shaded region?

1

Possible Answers:

Correct answer:

Explanation:

13

In order to find the area of the shaded region, we need to first find the areas of the triangle and the rectangle.

First, recall how to find the area of a triangle.

In the figure, we are given the triangle’s hypotenuse, which is also the width of the rectangle. We can then use this information and the Pythagorean theorem to find the length of the sides of the triangle.

Now, because this is a right isosceles triangle,

We can then make the following substitution:

Therefore:

Substitute in the value of the hypotenuse to find the length of the base:

Now, substitute this number in to find the area of the triangle.

Next, recall how to find the area of the rectangle:

Substitute in the given information from the question to find the area.

Now that we have the areas of both the rectangle and the triangle, we can find the area of the shaded region.

Solve.

Example Question #19 : How To Find The Length Of The Side Of A 45/45/90 Right Isosceles Triangle

In the figure, a right isosceles triangle is placed in a rectangle. What is the area of the shaded region?

2

Possible Answers:

Correct answer:

Explanation:

13

In order to find the area of the shaded region, we need to first find the areas of the triangle and the rectangle.

First, recall how to find the area of a triangle.

In the figure, we are given the triangle’s hypotenuse, which is also the width of the rectangle. We can then use this information and the Pythagorean theorem to find the length of the sides of the triangle.

Now, because this is a right isosceles triangle,

We can then make the following substitution:

Therefore:

Substitute in the value of the hypotenuse to find the length of the base:

Now, substitute this number in to find the area of the triangle.

Next, recall how to find the area of the rectangle:

Substitute in the given information from the question to find the area.

Now that we have the areas of both the rectangle and the triangle, we can find the area of the shaded region.

Solve.

Example Question #181 : 45/45/90 Right Isosceles Triangles

In the figure, a right isosceles triangle is placed in a rectangle. What is the area of the shaded region?

3

Possible Answers:

Correct answer:

Explanation:

13

In order to find the area of the shaded region, we need to first find the areas of the triangle and the rectangle.

First, recall how to find the area of a triangle.

In the figure, we are given the triangle’s hypotenuse, which is also the width of the rectangle. We can then use this information and the Pythagorean theorem to find the length of the sides of the triangle.

Now, because this is a right isosceles triangle,

We can then make the following substitution:

Therefore:

Substitute in the value of the hypotenuse to find the length of the base:

Now, substitute this number in to find the area of the triangle.

Next, recall how to find the area of the rectangle:

Substitute in the given information from the question to find the area.

Now that we have the areas of both the rectangle and the triangle, we can find the area of the shaded region.

Solve.

Example Question #182 : Triangles

In the figure, a right isosceles triangle is placed in a rectangle. What is the area of the shaded region?

4

Possible Answers:

Correct answer:

Explanation:

13

In order to find the area of the shaded region, we need to first find the areas of the triangle and the rectangle.

First, recall how to find the area of a triangle.

In the figure, we are given the triangle’s hypotenuse, which is also the width of the rectangle. We can then use this information and the Pythagorean theorem to find the length of the sides of the triangle.

Now, because this is a right isosceles triangle,

We can then make the following substitution:

Therefore:

Substitute in the value of the hypotenuse to find the length of the base:

Now, substitute this number in to find the area of the triangle.

Next, recall how to find the area of the rectangle:

Substitute in the given information from the question to find the area.

Now that we have the areas of both the rectangle and the triangle, we can find the area of the shaded region.

Solve.

Example Question #1161 : Plane Geometry

In the figure, a right isosceles triangle is placed in a rectangle. What is the area of the shaded region?

5

Possible Answers:

Correct answer:

Explanation:

13

In order to find the area of the shaded region, we need to first find the areas of the triangle and the rectangle.

First, recall how to find the area of a triangle.

In the figure, we are given the triangle’s hypotenuse, which is also the width of the rectangle. We can then use this information and the Pythagorean theorem to find the length of the sides of the triangle.

Now, because this is a right isosceles triangle,

We can then make the following substitution:

Therefore:

Substitute in the value of the hypotenuse to find the length of the base:

Now, substitute this number in to find the area of the triangle.

Next, recall how to find the area of the rectangle:

Substitute in the given information from the question to find the area.

Now that we have the areas of both the rectangle and the triangle, we can find the area of the shaded region.

Solve.

Example Question #184 : Triangles

In the figure, a right isosceles triangle is placed in a rectangle. What is the area of the shaded region?

6

Possible Answers:

Correct answer:

Explanation:

13

In order to find the area of the shaded region, we need to first find the areas of the triangle and the rectangle.

First, recall how to find the area of a triangle.

In the figure, we are given the triangle’s hypotenuse, which is also the width of the rectangle. We can then use this information and the Pythagorean theorem to find the length of the sides of the triangle.

Now, because this is a right isosceles triangle,

We can then make the following substitution:

Therefore:

Substitute in the value of the hypotenuse to find the length of the base:

Now, substitute this number in to find the area of the triangle.

Next, recall how to find the area of the rectangle:

Substitute in the given information from the question to find the area.

Now that we have the areas of both the rectangle and the triangle, we can find the area of the shaded region.

Solve.

Example Question #21 : How To Find The Length Of The Side Of A 45/45/90 Right Isosceles Triangle

In the figure, a right isosceles triangle is placed in a rectangle. What is the area of the shaded region?

7

Possible Answers:

Correct answer:

Explanation:

13

In order to find the area of the shaded region, we need to first find the areas of the triangle and the rectangle.

First, recall how to find the area of a triangle.

In the figure, we are given the triangle’s hypotenuse, which is also the width of the rectangle. We can then use this information and the Pythagorean theorem to find the length of the sides of the triangle.

Now, because this is a right isosceles triangle,

We can then make the following substitution:

Therefore:

Substitute in the value of the hypotenuse to find the length of the base:

Now, substitute this number in to find the area of the triangle.

Next, recall how to find the area of the rectangle:

Substitute in the given information from the question to find the area.

Now that we have the areas of both the rectangle and the triangle, we can find the area of the shaded region.

Solve.

Example Question #1172 : Basic Geometry

In the figure, a right isosceles triangle is placed in a rectangle. What is the area of the shaded region?

8

Possible Answers:

Correct answer:

Explanation:

13

In order to find the area of the shaded region, we need to first find the areas of the triangle and the rectangle.

First, recall how to find the area of a triangle.

In the figure, we are given the triangle’s hypotenuse, which is also the width of the rectangle. We can then use this information and the Pythagorean theorem to find the length of the sides of the triangle.

Now, because this is a right isosceles triangle,

We can then make the following substitution:

Therefore:

Substitute in the value of the hypotenuse to find the length of the base:

Now, substitute this number in to find the area of the triangle.

Next, recall how to find the area of the rectangle:

Substitute in the given information from the question to find the area.

Now that we have the areas of both the rectangle and the triangle, we can find the area of the shaded region.

Solve.

Example Question #186 : Triangles

In the figure, a right isosceles triangle is placed in a rectangle. What is the area of the shaded region?

9

Possible Answers:

Correct answer:

Explanation:

13

In order to find the area of the shaded region, we need to first find the areas of the triangle and the rectangle.

First, recall how to find the area of a triangle.

In the figure, we are given the triangle’s hypotenuse, which is also the width of the rectangle. We can then use this information and the Pythagorean theorem to find the length of the sides of the triangle.

Now, because this is a right isosceles triangle,

We can then make the following substitution:

Therefore:

Substitute in the value of the hypotenuse to find the length of the base:

Now, substitute this number in to find the area of the triangle.

Next, recall how to find the area of the rectangle:

Substitute in the given information from the question to find the area.

Now that we have the areas of both the rectangle and the triangle, we can find the area of the shaded region.

Solve.

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