In Δ ABC, ∠ A=60∘, BC=10 cm. Find the circumdiameter of the triangle. [sin 60∘=0.87]
Draw diameter BD passing through centre O, join CD
In Δ BCD, ∠ D=60∘ (Angle subtended by the same chord BC)
∠ BDC=90∘ (Angle subtended by diameter BD on circumference)
In right - angled triangle BCD
sin 60∘=BCBD=10BD
BD=10sin 60=100.87=11.49 cm
Hence circumdiameter = 11.49 cm