1. Proving Triangles Similar Same idea as polygons
Similar Triangles
Proving Triangles Similar
Same idea as polygons

2. Similar Triangles
Corresponding angles need to be congruent Corresponding sides need to be proportional All should have same scale factor You can write 2 column proofs like before, but we have to state sides proportional instead of congruent.

3. Similar Triangles
Given two angles measures of 70 and 45, each person draw a triangle using a protractor and straight edge – are the triangles similar can you prove they are (definition of similar) Give the measurements of 3 sides of a triangle as 5 cm, 8 cm and 10 cm, construct a triangle, if you use the same scale factor on all the sides and construct another triangle prove they similar (def) Given 2 sides and the included angle, 6 cm 9 cm and 65 degrees, construct a triangle, keeping the angle the same just changes the sides with the same scale factor construct another triangle, prove these triangles similar (def)

4. Proving Triangles Similar
AA – Angle Angle – if 2 corresponding angles are congruent then the third has to be congruent SSS – Side Side Side – all corresponding sides are proportional, same scale factor, same decimal SAS – Side Angle Side – if two sides of one triangle are proportional to two corresponding sides of another triangle and the included angle is congruent, then the triangles are similar

5. Are the triangles similar
Are the triangles similar. If yes then state the conjecture as to why and state the similarity statement (can you support the why what work or statements would you need), if no state why not.

6. Example

7. Example

9. Given the Alt of a Right Triangle
Notice the 3 similar triangles that are formed
Can you set up proportions that relate sides of large triangle to other two
What about a proportion that relates small and medium

10. Homework
Pg even and 13 State how triangles are similar