In adjoining figure o is the center of the circle.seg AB is diameter.at point CD is drawn from line BD is a tangent to the circle at point B then show that seg OD llchord AC
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Step-by-step explanation:
Given : O is the centre of the circle.
Seg AB is a diameter, CD is the tangent at C.
BD is a tangent at B
In ΔCOD and ΔBOD
⇒OC=OB ....(Radii of same circle)
⇒CD=DB ....(Tangent from an external point)
⇒OD=OD ....(Common side)
⇒ΔCOD=ΔBOD (SSS test)
⇒ΔCOD=ΔBOD=x (c.a.s.t.) equation (i)
In ΔAOC, AO=OC ....(Radii of same circle)
⇒ ∠OAC=∠OCA=y ....(Isoceles Δ theorem) equation (ii)
⇒∠COB=∠OAC+∠OCA ....(Remote interior ∠ theorem)
⇒∠COD+∠BOD=∠OAC+∠OCA
⇒x+x=y+y ....[From equation (i) and (ii)]
⇒2x=2y
⇒x=y ....(dividing by 2)
⇒∠COD=∠OCA
⇒ Seg OD∥ chord AC. ....(Alternate ∠s test)
Hence, proved.
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