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					 In a quadrilateral ABCD, with unequal sides if the diagonals AC and BD intersect at right angles, then
 
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-  AB² + BC² = CD² + DA² 
 -  AB² + CD² = BC² + DA² 
 -  AB² + AD² = BC² + CD²
 - AB² + BC² = 2(CD² + DA²)
 
 -  AB² + BC² = 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
