
Re: Nx2N lapped orthogonal transform
Posted:
Sep 3, 2013 11:51 AM


On 03/09/2013 10:32, James Dow Allen wrote: > James Dow Allen <gmail@jamesdowallen.nospam> might have writ, in > news:XnsA22175B33BFDDjamesdowallen@178.63.61.175: > >> Let >> ( A B 0 ) >> ( 0 A B ) >> ( B 0 A ) >> be a 3Nx3N real matrix with A,B,0 each NxN and 0 an allzeros matrix. >> >> What is the necessary and sufficient condition for that matrix to be >> orthogonal, i.e. that its transpose also be its inverse? >> >> This problem statement can be considered ambiguous. >> *But if you derive a good parametric form for (A B) you will know it.* >> >> (I already "know the answer." I post from curiosity: Is this a VERY easy >> problem, or just an easy problem?) > > James Dow Allen <gmail@jamesdowallen.nospam> might have writ, in > news:XnsA2236C8E3E26Ajamesdowallen@178.63.61.175: > >> I found it fruitful to introduce M = A + B; S = A  B
Both orthogonal, of course. So what about MS^{1} = MS^t? What can one say about that ... ?

