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In the adjoining figure, CE is drawn parallel to DB to meet AB produced at E. Prove that : ar (quad. ABCD) = ar (ΔDAE).

In the adjoining figure, CE is drawn parallel to DB to meet AB produced at E. Prove that : ar (quad. ABCD) = ar (ΔDAE). Quadrilaterals, R.S. Aggarwal Mathematics Solutions ICSE Class 9.

Theorems on Area

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Answer

We know that,

Triangles on the same base and between the same parallel lines are equal in area.

△ BDE and △ BDC lie on the same base BD and along the same parallel lines DB and CE.

∴ Area of △ BDE = Area of △ BDC …..(1)

From figure,

⇒ Area of △ ADE = Area of △ ADB + Area of △ BDE

⇒ Area of △ ADE = Area of △ ADB + Area of △ BDC [From equation (1)]

⇒ Area of △ ADE = Area of quadrilateral ABCD.

Hence, proved that △ ADE and quadrilateral ABCD are equal in area.

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