Answer:
Given,
∆ ABC is an isosceles triangle.
AB = AC = 13 cm
The altitude from A on BC meets BC at D.
D is the midpoint of BC.
AD = 5 cm
∆ ???????????? ???????????? ∆ ???????????? are right-angled triangles.
Applying Pythagoras theorem,
????????2 = ????????2 + ????????2
????????2 = ????????2 − ????????2
=>132 − 52
=>169 − 25
=>144
=>√144
=>12
BC = 2(BD)
=>2 × 12
=>24 cm.