1. 7-3: Proving Triangles are Similar
Rigor: 1) Prove 2 triangles are similar
2) Use similar triangles to solve indirect measurement problems
Relevance : Logic and proof, indirect measurement

2. Dissecting Similarity Statements
Turn to workbook page 298
Complete example 2 and the reflection problems on your own.
Be ready to discuss reflection questions in a few minutes

3. 3 Triangle Similarity Criterion
(AA ~) – If 2 pairs of corresponding angles are congruent, the ∆s are ~.
(SSS ~) – If all corresponding sides are proportional, the ∆s are ~.
(SAS ~) – If 2 pairs of corresponding sides are proportional and the included angle pair is congruent, the ∆s are ~.

4. EX 1: Are the triangles similar? Justify your answer.

5. EX 2: Prove that the triangles are similar.
A) B)

6. EX 3: 6)

7. Indirect Measurement: One of my favorite applications of Geometry!
One method of indirect measurement is using similarity proportions of triangles!
Used to calculate the height of pyramids & mountains, width of rivers, etc.
Ancient Greek philosopher Eratosthenes even used similar triangles to approximate the radius and circumference of the earth!
C = Syene, Egypt (now Aswan)
A = Alexandria
AE = shadow of the stick

8. EX 4: What is the height of the cliff?

9. EX 5: Using Indirect Measurement
A birdbath 2ft 6in tall casts an 18in shadow in a garden at the same time an oak tree casts a 90ft shadow. How tall is the tree?

10. 7-3 Classwork (graded)
Indirect measurement worksheet.
No work = no credit.

11. Secondary Assignment:
Honors: 7-3 Assignments
Primary Assignment: join.quizizz.com
Codes:
Period 1: (due Monday)
Period 5: (due Monday)
Period 6: (due Tuesday)
Secondary Assignment:
Workbook pg 301 and 302 ALL

12. Standard: 7-3 Assignments
Primary Assignment: join.quizizz.com
Codes:
Period 2: (due Tuesday)
Period 4: (due Tuesday)
Period 7: (due Monday)
Secondary Assignment:
Workbook pg 301 and 302 ALL