Section 4.3

I understand why RkQk = Qk*Qk Rk Qk but I wish that the labeling would be more consistant. When I first looked at the this equation I was extreamly confused as to why this equation would be true if Q was orthogonal which I assumed it would be since we were introduced to orthogonal matrices and QR factorization with Q being orthogonal matrices and introduced to unitary matrices with U. I think its interesting how a matrix, Ak, can converge to an upper triangle but that is a little harder to see how that is possible. I think the notation is kindof strange for (4.10) is that suppose to imply a limit? Other then that the material seems interesting and I wish there was more explanation as to what the function err does in Example 4.3.