5.1. Midsegment Theorem http://www.ck12.org
Guidance
Amidsegmentis a line segment that connects two midpoints of adjacent sides of a triangle. For every triangle there
are three midsegments. TheMidsegment Theoremstates that the midsegment of a triangle is half the length of the
side it is parallel to.
Example A
Draw the midsegmentDFbetweenABandBC. Use appropriate tic marks.
Find the midpoints ofABandBCusing your ruler. Label these pointsDandF. Connect them to create the
midsegment.
Don’t forget to put the tic marks, indicating thatDandFare midpoints,AD∼=DBandBF∼=FC.
Example B
Find the midpoint ofACfrom 4 ABC. Label itEand find the other two midsegments of the triangle.
Example C
Mark everything you have learned from the Midsegment Theorem on 4 ABC.
Let’s draw two different triangles, one for the congruent sides, and one for the parallel lines.