ACT Math : 45/45/90 Right Isosceles Triangles

Study concepts, example questions & explanations for ACT Math

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Example Questions

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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

这是一个triangle. 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 #1 :How To Find The Height Of A 45/45/90 Right Isosceles Triangle

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:

Example Question #1 :Isosceles Triangles

What is the area of an isosceles right triangle with a hypotenuse of?

Possible Answers:

Correct answer:

Explanation:

Now, this is really your standardtriangle. Since it is a right triangle, you know that you have at least one-degree angle. The other two angles must each bedegrees, because the triangle is isosceles.

Based on the description of your triangle, you can draw the following figure:

_tri101

This is derived from your reference triangle for thetriangle:

Triangle454590

对于我们的三角形,我们可能卡尔l one of the legs.We know, then:

Thus,

The area of your triangle is:

For your data, this is:

Example Question #1 :How To Find The Area Of A 45/45/90 Right Isosceles Triangle

What is the area of an isosceles right triangle with a hypotenuse of?

Possible Answers:

Correct answer:

Explanation:

Now, this is really your standardtriangle. Since it is a right triangle, you know that you have at least one-degree angle. The other two angles must each bedegrees because the triangle is isosceles.

Based on the description of your triangle, you can draw the following figure:

_tri111

This is derived from your reference triangle for thetriangle:

Triangle454590

对于我们的三角形,我们可能卡尔l one of the legs.We know, then:

Thus,

The area of your triangle is:

For your data, this is:

Example Question #7 :45/45/90 Right Isosceles Triangles

What is the area of an isosceles right triangle with a hypotenuse of?

Possible Answers:

Correct answer:

Explanation:

Now, this is really your standardtriangle. Since it is a right triangle, you know that you have at least one-degree angle. The other two angles must each bedegrees because the triangle is isosceles.

Based on the description of your triangle, you can draw the following figure:

_tri121

This is derived from your reference triangle for thetriangle:

Triangle454590

对于我们的三角形,我们可能卡尔l one of the legs.We know, then:

Thus,

The area of your triangle is:

For your data, this is:

Example Question #8 :45/45/90 Right Isosceles Triangles

is a right isosceles triangle with hypotenuse.What is the area of?

Possible Answers:

Correct answer:

Explanation:

Right isosceles triangles (also called "45-45-90 right triangles") are special shapes. In a plane, they are exactly half of a square, and their sides can therefore be expressed as a ratio equal to the sides of a square and the square's diagonal:

, whereis the hypotenuse.

In this case,maps to, so to find the length of a side (so we can use the triangle area formula), just divide the hypotenuse by:

So, each side of the triangle islong. Now, just follow your formula for area of a triangle:

Thus, the triangle has an area of

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

What is the perimeter of an isosceles right triangle with an hypotenuse of length?

Possible Answers:

Correct answer:

Explanation:

Your right triangle is atriangle. It thus looks like this:

_tri41

Now, you know that you also have a reference triangle fortriangles. This is:

Triangle454590

This means that you can set up a ratio to find.It would be:

Your triangle thus could be drawn like this:

_tri42

Now, notice that you can rationalize the denominator of:

Thus, the perimeter of your figure is:

Example Question #10 :45/45/90 Right Isosceles Triangles

What is the perimeter of an isosceles right triangle with an area of?

Possible Answers:

Correct answer:

Explanation:

Recall that an isosceles right triangle is also atriangle. Your reference figure for such a shape is:



Triangle454590or_tri51

Now, you know that the area of a triangle is:

For this triangle, though, the base and height are the same. So it is:

Now, we have to be careful, given that our area contains.Let's use, for "side length":

Thus,.现在的基础上,参考上图,你可以easily see that your triangle is:

_tri71

Therefore, your perimeter is:

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