Prove that the median from the vertex of an isosceles triangle is the bisector of the vertical angle.
Consider an isosceles triangle ABC having AD as the median and AB = AC.
Given AD is the median.
⇒ BD = DC
In Δ ABD and Δ ADC, we have
AB = AC
BD = DC
and AD = AD
Therefore, Δ ABD Δ ADC [SSS property]
⇒ ∠1 = ∠2 [cpct]
Hence, the median from the vertex of an isosceles triangle is the bisector of the vertical angle.