Two triangles are Similar if the only difference is size (and possibly the need to turn or flip one around). Show These triangles are all similar: (Equal angles have been marked with the same number of arcs) Some of them have different sizes and some of them have been turned or flipped. For similar triangles: All corresponding angles are equal and All corresponding sides have the same ratio Also notice that the corresponding sides face the corresponding angles. For example the sides that face the angles with two arcs are corresponding. Corresponding SidesIn similar triangles, corresponding sides are always in the same ratio. For example: Triangles R and S are similar. The equal angles are marked with the same numbers of arcs. What are the corresponding lengths?
Calculating the Lengths of Corresponding SidesWe can sometimes calculate lengths we don't know yet.
Step 1: Find the ratioWe know all the sides in Triangle R, and The 6.4 faces the angle marked with two arcs as does the side of length 8 in triangle R. So we can match 6.4 with 8, and so the ratio of sides in triangle S to triangle R is: 6.4 to 8 Now we know that the lengths of sides in triangle S are all 6.4/8 times the lengths of sides in triangle R. Step 2: Use the ratio
a faces the angle with one arc as does the side of length 7 in triangle R. a = (6.4/8) × 7 = 5.6 b faces the angle with three arcs as does the side of length 6 in triangle R. b = (6.4/8) × 6 = 4.8 Done!
Did You Know? Similar triangles can help you estimate distances. Copyright © 2017 MathsIsFun.com
In this lesson we’ll look at the ratios of similar triangles to find out missing information about similar triangle pairs. Similar trianglesIn 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.
Corresponding anglesIn 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.
Corresponding sidesIn 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 trianglesTo 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. Here we can say that ???\triangle XYZ\sim \triangle BCA???.
Example If the two triangles in the diagram are similar, solve for the variable.
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???
Example If ???\triangle XVY\sim \triangle XWZ???, solve for ???x???.
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??? Discover more from Krista King Math | Online math help |