In the given figure, a triangle ABC is drawn to circumscribe a circle of radius 3 cm such that the segments BD and DC into which BC is divided by the point of contact D are, of lengths 6 cm and 9 cm respectively. If the area of △ABC = 54 cm2 then find the lengths of sides of AB and AC.
Construction: Join OA, OB, OC, OE ⊥ AB at E and OF ⊥ AC at F
We know that tangent segments to a circle from the same external point are congruent.
Now, we have
AE = AF, BD = BE = 6 cm and CD = CF = 9 cm
Now,
Area △ABC = Area △BOC + Area △AOB + Area △AOC
⇒54=12×BC×OD+12×AB×OE+12×AC×OF [Radius ⊥ Tangent]
⇒108=15×3+(6+x)×3+(9+x)×3
⇒36=15+6+x+9+x
⇒36=30+2x
⇒2x=6
⇒x=3 cm
∴AB=6+3=9 cm and AC=9+3=12 cm