Let A be an m n matrix of rank n and let P = A(ATA) 1AT . (a) Show that Pb = b for every b R(A). Explain this property in terms of projections. (b) If b R(A) , show that Pb = 0. (c) Give a geometric illustration of parts (a) and (b) if R(A) is a plane through the origin in R3. 1

L7 - 2 Def. One-Sided Limits We say that a functio fn(x)asm t L as x approaches the numberc from the right if we can make every value of f(x) as close to L as we want by choosing x suﬃciently close to c but x>c . We write thir sight-hand limit...