In a triangle ABC, AB = AC. D is the midpoint of BC. P is any point of BC. Then
. O is any point in the interior of a triangle ABC. Prove that
1. AB + AC > OB + OC
2.AB + BC + CA > OA + OB + OC
3.OA + OB + OC > 1/2(AB + AC + BC)
In any triangle ABC, (AB - AC) > BC.
In a triangle ABC, D is the midpoint of AB, E is the midpoint of AC and DE is parallel to BC, then DE : BC = ________.