Given l1 is the perpendicular bisector of BC.
∴ ∠SMC = 90° and BM = MC
BC = 12 cm
⇒ BM + MC = 12 cm
MC + MC = 12 cm [∴ BM = MC]
2MC = 12
MC = 122
MC = 6 cm
Given SM = 8 cm
By Pythagoras theorem SC2 = SM2 + MC2
SC2 = 82 + 62
SC2 = 64 + 36
CS2 = 100
CS2 = 102
CS = 10 cm