Section 4.2- Triangle Congruence by SSS and SAS
Essential Question: How can we determine whether figures are congruent?
Do Now:
Recall: Distance Formula= √(𝑥2 − 𝑥1 )2 + (𝑦2 − 𝑦1 )2
Find the lengths of BC and FD. Find the lengths of AC and EF.
NOTE:
In section 4.1, you proved that two triangles are congruent by showing ______
________________ parts congruent. However, this is ________ _______________ than
you need to prove triangles ______________.
Method 1 to Prove Triangles Congruent
Name of Theorem
If…
Then…
three sides of one triangle are congruent to
three sides of another triangle, then the two
triangles are __________________.
Δ ABC≅ ________
Name the corresponding ≅ segments:
Example 1: Using SSS ≅
Method 2 to Prove Triangles Congruent
Name of Theorem
If…
Then…
two sides and the
____________________________ of one
triangle are congruent to two sides and the
included angle of another triangle
the two triangles
are
________________.
Look at the figures to fill in the blanks below.
Example 2: Using SAS
What other information do you need to prove ΔLEB ≅ ΔBNL by SAS?
Problem 3: Identifying Congruent Triangles
Would you use SSS or SAS to prove the triangles below congruent? Explain.
Group Work:
Begin the Practice Proofs on SSS ≅ and SAS ≅.
HW: p. 230-231 #8, 11-14, 18, 19, 24-26; Complete the practice proofs.