The sides of a quadrilateral ABCD are AB=13cm,BC=16cm,CD=20cm and DA=5cm. If BD=12cm,find the area of the quadrilateral, using Heron's formula.
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Solution
Consider ΔABD : s = (13 + 5 + 12)/2 cm s = 15 cm By heron formula, Area of ΔABC =√15×(15−13)×(15−5)×(15−12) cm² = 30 cm² Consider ΔBCD : s = (16 + 20 + 12)/2 cm s = 24 cm By heron formula, Area of ΔBCD =√24×(24−16)×(24−20)×(24−12) cm² = 96 cm² Area of quadrilateral ABCD = Area of ΔABC + Area of ΔBCD = (30 + 96) cm² = 126 cm²