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  1. In a quadrilateral ABCD, with unequal sides if the diagonals AC and BD intersect at right angles, then
    1. AB² + BC² = CD² + DA²
    2. AB² + CD² = BC² + DA²
    3. AB² + AD² = BC² + CD²
    4. AB² + BC² = 2(CD² + DA²)
Correct Option: B

On the basis of question we draw a figure of quadrilateral ABCD

OB² + OC² = BC²

OC² + OD² = CD²

OD² + OA² = AD²

OA² + OB² = AB²
Pythagoras theorem

∴ 2 (OB² + OA² + OD² + OC²) = AB² + BC² + CD² + DA²
⇒ 2(AB² + CD²) = AB² + BC² + CD² + DA²
⇒ AB² + CD² = BC² + DA²



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