1) This document discusses midsegments of triangles, including examples of finding missing parts of a triangle where one side is a midsegment, calculating the perimeter when three sides are midsegments, and proving two triangles are congruent when points D, E, and F are midpoints. 2) It provides an example problem to find missing parts of a triangle where one side is a midsegment, and asks students to prove two triangles are congruent given points D, E, and F are midpoints using corresponding angles and the definition of a midpoint. 3) The exit slip asks students to state the "Midsegment Theorem".

1. Midsegment of a Triangle
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2. A
B C
D E
Ex. 1) DE is the midsegment of triangle
ABC. Find the missing parts.
12
47°
110°
X
y

3. Ex. 2) Find the perimeter of ∆ABC
if DE, DF, and FE are midsegments.

4. Ex. 3) Given: D, E, and F are midpoints.
Prove: ∆ADE≅∆EFC
Statements Reasons
1. D, E, F are midpoints Given
2. DE and EF are
midsegments
Def. of midsegment
3. DE || BC; EF || AB Midsegment is parallel to third side.
4. ∠1≅∠2; ∠3≅∠2;
∠4≅∠C
Corresponding Angles
4. ∠1≅∠3 Transitive Property
5. AE≅EC Def. of midpoint
6. ∆ADE≅∆EFC AAS

5. Exit Slip:
What is the "Midsegment
Theorem"?