Proving Triangles Congruent: SSS and

SASUnit 1B2 Day 5

Tell whether each statement is needed to

show congruence. (yes or no) The figures must have exactly the same size. The figures must have exactly the same

location. The figures must have exactly the same shape. The figures must be triangles. The figures must be polygons.

Do now

Before, we learned that if all three ____________

and all three _____________ of two triangles are congruent, then _____________________________

But there are easier ways to prove congruence!

Triangle Congruence

If three sides of one triangle are congruent to

three sides of a second triangle, then the two triangles are congruent.

Side-Side-Side Congruence Postulate

(post. 19)

Prove that ΔABC ≅ ΔDEC.

Ex. 1: SSS

Prove that ΔPQW ≅ ΔPSW.

Ex. 2: SSS

If two sides and the included angle of one

triangle are congruent to two sides and the included angle of a second triangle, then __________________________ _____ is includes between sides _______ and

_____

Side-Angle-Side Congruence Postulate

(post. 20)

Ex. 3: Prove that ΔABC ≅ ΔDEC.

Ex. 3: SAS

Which congruence postulate could you

use to prove that ΔABC ≅ ΔABD?

Ex. 4: Which Postulate to Use

Given: CD | AB, CB ≅ BD. Prove: ΔABC ≅ ΔABD.

Ex. 5: Which Postulate to Use

Shared sides or angles – ____________________

X-shape – ___________________

Perpendicular – _________________

Things to Look For

Closure