Similar triangles have corresponding sides and angles — Krista King Math | Online math help (2024)

Similar triangles have corresponding sides and angles — Krista King Math | Online math help (1)

Similar triangles have corresponding angles and corresponding sides

In this lesson we’ll look at the ratios of similar triangles to find out missing information about similar triangle pairs.

Similar triangles

In a pair of similar triangles, corresponding sides are proportional and all three angles are congruent. This means if you know two triangles are similar to one another you can use the information to solve for missing parts.

Similar triangles have corresponding sides and angles — Krista King Math | Online math help (2)

Corresponding angles

In a pair of similar triangles the corresponding angles are the angles with the same measure. In the diagram of similar triangles, the corresponding angles are the same color.

Similar triangles have corresponding sides and angles — Krista King Math | Online math help (3)

Corresponding sides

In a pair of similar triangles, the corresponding sides are proportional. Corresponding sides touch the same two angle pairs.

When the sides are corresponding it means to go from one triangle to another you can multiply each side by the same number.

In the diagram of similar triangles the corresponding sides are the same color.

Naming similar triangles

To show two triangles are similar, you use the symbol ???\sim???. You need to match the letters from the first triangle to the angles with the corresponding vertices on the second triangle.

Similar triangles have corresponding sides and angles — Krista King Math | Online math help (5)

Here we can say that ???\triangle XYZ\sim \triangle BCA???.

When triangles are similar, you can use that fact to solve for the value of angles and sides

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Similar triangles have corresponding sides and angles — Krista King Math | Online math help (7)

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Solving for the variable in two similar triangles

Example

If the two triangles in the diagram are similar, solve for the variable.

Similar triangles have corresponding sides and angles — Krista King Math | Online math help (8)

In similar triangles, corresponding sides are proportional. In the diagram, ???x??? corresponds to ???8???, and ???42.5??? corresponds to ???17???. So we say

???\frac{x}{8}=\frac{42.5}{17}???

???17x=8(42.5)???

???17x=340???

???x=20???

Similar triangles have corresponding sides and angles — Krista King Math | Online math help (9)

How to solve for values in similar triangles

Example

If ???\triangle XVY\sim \triangle XWZ???, solve for ???x???.

Similar triangles have corresponding sides and angles — Krista King Math | Online math help (10)

In similar triangles, corresponding sides are proportional. In the diagram, ???4x+12??? corresponds to ???88???, and ???91??? corresponds to ???143???.

???\frac{4x+12}{88}=\frac{91}{143}???

???(4x+12)143=91(88)???

???(4x+12)143=8,008???

???\frac{(4x+12)143}{143}=\frac{8,008}{143}???

???4x+12=56???

???4x=44???

???x=11???

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Similar triangles have corresponding sides and angles — Krista King Math | Online math help (2024)

FAQs

What are similar triangles corresponding sides and angles? ›

Similar triangles are triangles that have the same shape, but their sizes may vary. All equilateral triangles, squares of any side lengths are examples of similar objects. In other words, if two triangles are similar, then their corresponding angles are congruent and corresponding sides are in equal proportion.

Are corresponding sides proportional? ›

Corresponding sides have lengths that are proportional. Corresponding angles are congruent.

How to find corresponding sides? ›

If you superimpose two shapes, the sides that overlap on each other will be corresponding sides. Corresponding sides touch the same two angle pairs of two figures. Also, the angles formed by two corresponding sides are corresponding angles.

How to find the missing angles of similar triangles? ›

As a general rule, the angles of a triangle always add to 180 degrees. To calculate a missing angle, you add the other two angles, and then subtract that sum from 180.

What is the ratio of corresponding sides similar triangles? ›

If two triangles are similar, then all three of their angles are congruent to each other, and their corresponding sides are in proportion. This means that the ratio of their corresponding sides are equal to each other.

When two triangles are similar then their corresponding sides are proportional? ›

Two triangles are said to be similar if their corresponding angles are congruent and the corresponding sides are in proportion . In other words, similar triangles are the same shape, but not necessarily the same size. The triangles are congruent if, in addition to this, their corresponding sides are of equal length.

What is the formula for corresponding sides of similar triangles are proportional? ›

Hence, if two triangles are similar, then their corresponding sides are proportional. Thus we conclude that if △ABC≃DEF △ ABC ≃ DEF , then we say that the corresponding sides are proportional and the angles are equal.

What is the short form for corresponding angles of similar triangles? ›

Similar triangles have the same corresponding angle measures and proportional side lengths. The triangle similarity criteria are: AA (Angle-Angle) SSS (Side-Side-Side)

What is the proof of corresponding sides of similar triangles? ›

If two triangles are similar, then the ratio of their areas is the square of the ratio of any two corresponding sides; that is, if ∆ABC ~ ∆DEF and AB = r · DE, then α(∆ABC) = r2 · α(∆DEF). Proof.

Are corresponding sides always congruent? ›

Since rigid transformations preserve distance and angle measure, all corresponding sides and angles are congruent. That means that one way to decide whether a pair of triangles are congruent would be to measure all of the sides and angles. The triangle congruence criteria give us a shorter way!

What are the rules for similar triangles? ›

If you have two right triangles and the ratio of their hypotenuses is the same as the ratio of one of the sides, then the triangles are similar. (You know the missing side using the Pythagorean Theorem, and the missing side must also have the same ratio.)

What are angles in the same position called? ›

Two angles in the same position are called corresponding angles. They have the same measure if the original two lines are parallel.

Are corresponding angles equal? ›

If two parallel lines are cut by a transversal, each pair of corresponding angles is equal in measure. Corresponding angles lie on the same side of the transversal in corresponding positions.

What are matching sides in similar triangles? ›

Two triangles are said to be similar, if their corresponding angles are equal and corresponding sides are proportional i.e., the ratios between the lengths of the corresponding sides are equal.

When two triangles are similar the corresponding sides are equal? ›

When two triangles are similar, their corresponding angles are equal and their corresponding sides are proportional.

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