Basic Geometry : 45/45/90 Right Isosceles Triangles

Study concepts, example questions & explanations for Basic Geometry

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Example Questions

Example Question #191 : Triangles

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

10

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 #192 : 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?

11

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 #193 : 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?

12

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 #191 : 45/45/90 Right Isosceles Triangles

If the length of one leg of a right isosceles triangle is 16cm, what is the length of the other leg?

Possible Answers:

Correct answer:

Explanation:

First we need to know that a right isosceles triangle has two legs with the same length.

In this case we do not need to worry about the hypotenuse.

Since one leg measures 16 cm, the other leg is the same length and so our answer is 16cm.

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