Download 7.3 Proving Triangles Similar – Notes Name: Geometry Mrs. Elmore

7.3 Proving Triangles Similar – Notes
Geometry
Mrs. Elmore
Name: _______________________
Period: _____ Date: ___________
Proving Triangles Similar
Angle-Angle Similarity (AA~)
If two angles of one triangle are _________________ to
two angles of another triangle, then the triangles are
Similarity statement:
similar.
Side-Angle-Side Similarity (SAS~)
If an angle of one triangle is _______________ to an
angle of a second triangle, and the sides including the
two angles are _______________, then the triangles are
Similarity statement:
similar.
Side-Side-Side Similarity (SSS~)
If the corresponding sides of two triangles are
_____________________, then the triangles are similar.
Similarity statement:
Practice
Are the triangles similar? If so, name the postulate or theorem you used. If not, explain.
1.
2.
Hint: redraw as two separate triangles.
Explain why the triangles are similar. Then find the value of x.
3.
4.
Indirect Measurement
You can use similar triangles and measurements to find distances that are difficult to measure
directly. This is called indirect measurement.
Two Methods of Indirect Measurement:
1) Use the fact that light reflects off a mirror at the same angle at which it hits the mirror.
2) Use the similar triangles that are formed by certain figures and their shadows.
Practice
Use indirect measurement to solve the problem.
5.
6. In sunlight, a cactus casts a 9-ft shadow. At the same time a person 6 ft tall casts a 4-ft
shadow. Use similar triangles to find the height of the cactus.