7-3: Identifying Similar Triangles
Expectations:G2.3.2: Use theorems about congruent
triangles to prove additional theorems and solve problems.
G2.3.3: Prove that triangles are similar by SSS, SAS and AA conditions for similarity.
04/19/23 7-3 Similar Triangles
Angle-Angle a. Draw two triangles with angle
measures of 75° and 65°.
b. Label the 75° angles ∠A and ∠X.
c. Label the 65° angles ∠B and ∠Y.
04/19/23 7-3 Similar Triangles
Angle-Angle d. Compare the ratios of corresponding sides.
e. What does this tell us about the triangles?
04/19/23 7-3 Similar Triangles
Angle-Angle Triangle Similarity Theorem
If two angles of a first triangle are congruent to two angles of a second triangle, then the triangles are similar.
04/19/23 7-3 Similar Triangles
Side-Side-Side a. Draw ∆ABC such that AB = 4,
BC = 6 and AC = 7.b. Draw ∆DEF such that DE = 8,
EF = 12 and DF = 14.
04/19/23 7-3 Similar Triangles
Side-Side-Side c. Compare corresponding angles.
d. What is true about the triangles?
04/19/23 7-3 Similar Triangles
Side-Side-Side Triangle Similarity Theorem
If the measures of the corresponding sides of 2 triangles are proportional, then the triangles are similar.
04/19/23 7-3 Similar Triangles
Side-Angle-Side a. Draw ∆KLM such that KL = 4,
LM = 5 and m∠L = 60°.
b. Draw ∆RST such that RS = 8, ST = 10 and m∠S = 60°.
04/19/23 7-3 Similar Triangles
Sid-Angle-Side Triangle Similarity Theorem
If the measures of two sides of one triangle are proportional to two sides of a second triangle and the included angles are congruent, then the triangles are similar.
04/19/23 7-3 Similar Triangles
Equality Properties of Similarity
Similarity of figures is reflexive, symmetric and transitive.
04/19/23 7-3 Similar Triangles
Are the following triangles similar? Justify your response.
20 12
15
7.212
9
04/19/23 7-3 Similar Triangles
Are the triangles below similar? Justify with a postulate or
theorem.
04/19/23 7-3 Similar Triangles
If AB // EF, AD = 9, DB = 16, EC = 2(AE), determine AE, AC, BC and
EF
A D B
FHE
C
04/19/23 7-3 Similar Triangles
Use similar triangles to answer the question below.
At 4:00 a yard stick cast a 5 foot shadow. How tall is a tree that has an 18 foot shadow at the same time?
04/19/23 7-3 Similar Triangles
In the figure below, segment AB ⊥ segment DE. The measure of ∠CAD is equal to the measure of ∠CEB. The length of segment CA is 6 units and the length of segment CE is 187 units. If the length of segment AD is 10 units, what is the length of segment EB?
A.10B.20C.25D.30E. 35
04/19/23 7-3 Similar Triangles
A
10
D
C
18
E
B
6