ACT Math : How to find the height of a 45/45/90 right isosceles triangle

Study concepts, example questions & explanations for ACT Math

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Example Questions

Example Question #1 :45/45/90 Right Isosceles Triangles

The area of an isosceles right triangle is. What is its height that is correlative and perpendicular to a side that is not the hypotenuse?

Possible Answers:

Correct answer:

Explanation:

Recall that an isosceles right triangle is atriangle. That means that it looks like this:

_tri11

This makes calculating the area very easy! Recall, the area of a triangle is defined as:

However, sincefor our triangle, we know:

Now, we know that. Therefore, we can write:

Solving for, we get:

This is the length of the height of the triangle for the side that is not the hypotenuse.

Example Question #2 :45/45/90 Right Isosceles Triangles

What is the area of an isosceles right triangle that has an hypotenuse of length?

Possible Answers:

Correct answer:

Explanation:

Based on the information given, you know that your triangle looks as follows:

_tri21

This is atriangle. Recall your standardtriangle:

Triangle454590

You can set up the following ratio between these two figures:

Now, the area of the triangle will merely be(since both the base and the height are). For your data, this is:

Example Question #3 :45/45/90 Right Isosceles Triangles

Find the height of an isoceles right triangle whose hypotenuse is

Possible Answers:

Correct answer:

Explanation:

To solve simply realize the hypotenuse of one of these triangles is of the formwhere s is side length. Thus, our answer is.

Example Question #4 :45/45/90 Right Isosceles Triangles

The area of an isosceles right triangle is. What is its height that is correlative and perpendicular to this triangle's hypotenuse?

Possible Answers:

Correct answer:

Explanation:

Recall that an isosceles right triangle is atriangle. That means that it looks like this:

_tri11

This makes calculating the area very easy! Recall, the area of a triangle is defined as:

However, sincefor our triangle, we know:

Now, we know that. Therefore, we can write:

Solving for, we get:

However, be careful! Notice what the question asks: "What is its height that is correlative and perpendicular to this triangle's hypotenuse?" First, let's find the hypotenuse of the triangle. Recall your standardtriangle:

_tri51

Since one of your sides is, your hypotenuse is.

Okay, what you areactuallylooking for isin the following figure:

_tri61

Therefore, since you know the area, you can say:

Solving, you get:.

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