Daniel

answers: 1

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Answer:

△ABC is an equilateral triangle

AB=BC=CA=9cm

O is the circumcentre of △ABC

∴OD id the perpendicular of the side BC

In △OBD and △ODC

OB=OC (Radius of the circle)

BD=DC (D is the mid point of BC)

OD=OD (common)

∴△OBD=△ODC

⇒∠BOD=∠COD

∠BOC=2∠BAC=2×60

∘ =120

(The angle subtended by an arc at the center is double the angle subtended by it at any point on the remaining part of the circle)

∴∠BOD=∠COD= 2

∠BOC = 2

120 =60

BD=BC= 2

BC = 29cm

In △BOD

⇒sin∠BOD=sin60

= OB, BD

402

Laura Rogers

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