InterviewSolution
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In the adjacent figure, if AB = 12 cm, BC = 8 cm and AC = 10 cm, then AD =A. 5 cmB. 4 cm C. 6 cmD. 7 cm |
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Answer» Answer is D. 7 cm Given: AB = 12 cm BC = 8 cm AC = 10 cm Property: If two tangents are drawn to a circle from one external point, then their tangent segments (lines joining the external point and the points of tangency on circle) are equal. By the above property, AD = AF (tangent from A) BD = BE (tangent from B) CF = CE (tangent from C) Clearly, AB = AD + DB = 12 cm BC = BE + EC = 8 cm AC = AF + FC = 10 cm Now, AB – BC = 12 cm – 8 cm ⇒ (AD + DB) – (BE + EC) = 12 cm – 8 cm ⇒ AD + DB – BE – EC = 12 cm – 8 cm ⇒ AD + BE – BE – CF = 12 cm – 8 cm [∵ DB = BE and CF = CE] ⇒ AD – CF = 12 cm – 8 cm ⇒ AD – (10 cm – AF) = 12 cm – 8 cm [∵AF + FC = 10 cm ⇒ FC = 10 cm – AF] ⇒ AD – (10 cm – AF) = 4 cm ⇒ AD – 10 cm + AF = 4 cm ⇒ AD + AD = 4 cm + 10 cm [∵ AD = AF] ⇒ 2AD = 14 cm ⇒ AD = \(\frac{14cm}{2}\) ⇒ AD = 7 cm Hence, AD = 7 cm |
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