Asked by NikhilD | 8th Jun, 2010, 07:09: PM

Expert Answer:

Dear Student,
The equation of one of the diagonals is given.
x - y = alpha.
=> y = x - alpha
Now, the diagonals of a square are perpendicular. And if two lines are perpendicular, then their slopes m1 and m2, have property that m1m2 = -1. ----(1)
let m be the slope of the required diagonal and 1 is the slope of given diagonal.
from (1), we get
m = -1
Now, the required diagonal's equation is
y = -x + c (where c is unknown)
But we have been given one of the points (alpha, beta) on this diagonal.
=> beta = -alpha + c
=> c = alpha + beta
Hence the eqn of diagonal becomes
y = -x + alpha + beta ----(2)
Now, None of the options provided in your question satisfy this equation. Please check the options again, and the one which satisfies this eqn (2), shall be the correct answer.

Answered by  | 15th Jul, 2010, 02:19: PM

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