

InterviewSolution
Saved Bookmarks
1. |
If A is any square matrix such that `A+I/2` and `A-I/2` are orthogonal matrices, thenA. A is orthogonalB. A is skew- symmetric matrix of even orderC. `A^(2)= 3/4 I`D. None of these |
Answer» Correct Answer - B `because (A-1/2I)(A-1/2)^(T)=I ` ...(i) and `because (A+1/2I)(A+1/2)^(T)=I ` ...(ii) `rArr (A-1/2I)(A^(T)-1/2)=I ` and `rArr (A+1/2I)(A^(T)+1/2)=I ` `rArr A + A^(T) = 0 ` [subtracting the two results] ` rArr A^(T) = - A` `therefore` A is skew-symmetric matrix. From first result, we get `A A ^(T) = 3/4 I` `rArr A^(2) = - 3/4 I` `therefore abs(A^(2) ) = abs(-3/4I)` `therefore abs(A)^(2) = (-3/4)^(n)` `rArr n` is even. |
|