IXL | Angle-angle criterion for similar triangles

△

and

△

are shown below.

Which statement is true?

△

is similar to

△

is not similar to

△

There is not enough information to determine whether the triangles are similar.

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Learn with an example

question

△

and

△

are shown below.

Which statement is true?

△

is similar to

△

is not similar to

△

There is not enough information to determine whether the triangles are similar.

key idea

Angle-angle criterion for similar triangles
If two angles in one triangle are congruent to corresponding angles in another triangle, then the triangles are similar.

solution

To determine whether

△

and

△

are similar, start by finding the measure of

∠

You know that

∠

and

∠

So, you can solve for

∠

by setting the sum of the angle measures in

△

equal to

180

∠

180

∠

180

∠

108

180

∠

The angles in

△

are

and

Notice that

△

also has two angles that are each

Since

△

and

△

have two pairs of congruent corresponding angles,

△

is similar to

△

Looking for more? Try these:

Lesson: Similar triangles

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Teacher tools

Work it out

Not feeling ready yet? These can help:

S.5Identify similar triangles

Q.9Triangle Angle-Sum Theorem

Lesson: Similar triangles

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