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A quadrilateral ABCD is drawn to circumscribe a circle (see the fig. given below). Prove that AB + CD = AD + BC. |
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Answer» Data: In the quadrilateral, ABCD is drawn to circumscribe a circle. To Prove: AB + CD = AD + BC The lengths of tangents drawn from an extrenal point to a circle are equal. ∴ Tangents AP and AS are drawn from point A. ∴ AP = AS Tangents BP and BQ are drawn from point B. ∴ BP = BQ Tangents CQ, CR are drawn from point C. ∴ CQ = CR. Tangents DR, DS are drawn from point A. ∴ DR = DS L.H.S.: AB + CD = AP + PB + CR + RD = AS + BQ + CQ + DS = AS + SD + BQ + CQ ∴ AB + CD = AD + BC ∴ L.H.S. = R.H.S. |
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