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A/sinA=B/sinB
A/sin60°=4/sin45°
A/1/2√3=4/1/2√2
A=4√3/√2.√2/√2
A=2√6cm

AC/(sin 45°) = BC/(sin 60°)
4/(1/2 √2) = BC/(1/2 √3)
4/√2 = BC/√3
√2 BC = 4√3
BC = (4√3)/√2 . √2/√2 = (4√6)/2 = 2√6 cm