Midsegments of triangles
key notes :
π Midsegments of Triangles π
Definition
A midsegment of a triangle is a line segment that connects the midpoints of two sides of a triangle.
βοΈ Think of it as the “middle connector”!
Key Properties β
Parallel to the third side
- The midsegment is always parallel to the side of the triangle that it does not touch.
- π’ Example: If AB and AC are sides, and D and E are their midpoints, then DE β₯ BC.
Half the length of the third side
- The length of the midsegment = Β½ Γ length of the side it is parallel to.
- β¨ Formula: DE = Β½ Γ BC
Forms a smaller triangle inside
- Two midsegments can form a triangle inside the original triangle, similar to the main triangle.
How to Identify a Midsegment π
- Look for points exactly halfway along two sides.
- Connect them with a straight line.
- Check if it is parallel to the third side and half its length.
Uses of Midsegments π οΈ
- Helps in finding missing lengths in triangles.
- Used in coordinate geometry to find midpoints and slope relationships.
- Makes triangles similar and proves congruence in parts of triangles.
Fun Visual Tip π¨
- Draw a triangle π
- Mark midpoints of two sides πΉ
- Connect them πΈ
- Notice how the midsegment forms a mini parallel line inside the triangle
β Remember:
- Midsegment = connects midpoints
- Parallel to third side β₯
- Length = Β½ of third side
Learn with an example
SU is a midsegment of β³TVW.
If VW = 44, what is SU?

SU =
SU is a midsegment of β³TVW.

So, SU is half of VW. Set SU equal to half of VW and solve for SU.
SU = VW/2
= 44/2 —> Plug in VW=44
= 22 —> Divide
So, SU = 22.
If PR = 20, what is ST?

ST = ____
Since P is the midpoint of QT and R is the midpoint of QS . PR is a midsegment of β³QST.

So, PR is half of ST. In other words, ST is twice PR. Set ST equal to twice PR and solve for ST.
ST= 2 . PR
= 2(20) Plug in PR = 20
= 40 Multiply
So, ST = 40.
If PR = 35, what is ST?

ST =
Since PT β PQ and RS β QR , PR is a midsegment of β³QST.

So, PR is half of ST. In other words, ST is twice PR. Set ST equal to twice PR and solve for ST.
ST = 2 . PR
= 2(35) Plug in PR = 35
= 70 Multiply
So, ST=70.
Let’s practice!βοΈ

