1. Lesson 7 – 3 Similar Triangles
Geometry
Lesson 7 – 3
Similar Triangles
Objective:
Identify similar triangles using the AA Similarity postulate and the
SSS and SAS Similarity Theorem.
Use similar triangles to solve problems.

2. Similar Triangles Angle-Angle (AA) Similarity
If two angles of one triangle are congruent to two angles of another triangle, then the triangles are similar.

3. Determine whether the triangles are similar
Determine whether the triangles are similar. If so, write a similarity statement. Explain your reasoning. 48 75
JKL ~ QPM
By AA similarity.
SRX ~ SWT
By AA similarity

4. JKL ~ PQL 46 43 No triangles are not similar since there
Determine whether the triangles are similar. If so, write a similarity statement. Explain your reasoning. 46 43
No triangles are not
similar since there
are no 2 angles the
same.
JKL ~ PQL
By AA similarity

5. Theorem Side-Side-Side (SSS) Similarity
If the corresponding side lengths of two triangles are proportional, then the triangles are similar.

6. Theorem Side-Angle-Side (SAS) Similarity
If the lengths of two sides of one triangle are proportional to the lengths of two corresponding sides of another triangle and the included angles are congruent, then the triangles are similar.

7. 0.4 = 0.4 0.4 = 0.4 0.4 = 0.4 PQR ~ STR By SSS similarity
Determine whether the triangles are similar. If so, write a similarity statement. Explain.
0.4 = 0.4
0.4 = 0.4
0.4 = 0.4
PQR ~ STR
By SSS similarity

8. Determine whether the triangles are similar
Determine whether the triangles are similar. If so, write a similarity statement. Explain.

9. A. Uses SAS similarity
C. Uses AA similarity
D. Uses SSS similarity
Does not have a congruent included angle.
No similarity

10. B is the only choice that satisfies a similarity
condition. SSS similarity.

11. AEF ~ ACB By SAS Similarity
Determine whether the triangles are similar. If so, write a similarity statement. Explain.
AEF ~ ACB
By SAS Similarity

12. Find BE and AD 10.5 = 5x 2.1 = x BE = 2.1 AD = 4.5 + 3 = 7.5
Whole side
of one triangle
to whole side
of other triangle.
10.5 = 5x
2.1 = x
BE = 2.1
AD = = 7.5
3y + 9 = 5y
9 = 2y
4.5 = y

13. Find QP and MP 48 = 30 + 6x 18 = 6x 3 = x QP = 3 QP = 3 MP = 8

14. Find WR and RT WR = x + 6 = 8 RT = 2x + 6 = 10 10x + 60 = 16x + 48

15. The Palmetto building is
Real world
Adam is standing next to the Palmetto Building in Columbia, South Carolina. He is 6 feet tall and the length of his shadow is 9 feet. If the length of the shadow of the building is feet, how tall is the building?
The Palmetto building is
215 feet tall.
9x = 1935
x = 215

16. Homework
Pg – 8 all, 10 – 24 E, 38, 42 – 56 E