Problem
GEO-B1-M03-P003 Length of a Midline
#3
★☆☆☆☆ Level 1 of 5
In triangle \(ABC\), points \(M\) and \(N\) are the midpoints of sides \(AB\) and \(AC\). It is known that \(BC=18\). Find \(MN\).
A midline of a triangle equals half of the third side.
Segment \(MN\) is a midline of triangle \(ABC\). Therefore \(MN=\frac{1}{2}BC=9\).
A quick check of the midline theorem.