Question

Let ABCD be a square with sides of unit lenght. Points E and F are taken on sides AB and AD, respectively,so that `AE=AF`. Let P be a point inside the squre ABCD.
The value of `(PA)^2-(PB)^2+(PC)^2-(PD)^2` is equal to
A. 3
B. 2
C. 1
D. 0

Answer 1

Correct Answer - D

`(PA)^2-(PB)^2+(PC)^2-(PD)^2`
`=(alpha^2+gamma ^2)-(alpha^2+delta^2)+(delta^2+beta^2)-(gamma^2+beta^2)=0`