
orthogonality
Consider vectors v1, v2, v3 in R^4; we are told that (vi dot vj) is the entry aij of matrix A. A =
[3 5 11]
[5 9 20]
[11 20 49].
Find length of (v1 + v2). For this I got 2(sqrt(3)). Can someone check this?
Also, find projV(v3), where V = span(v1, v2). Express your answer as a linear combination of v1 and v2.

Can you post your work so we can check it?

v1 + v2 = sqrt((v1 dot v1) + (v2 dot v2)) = sqrt((a11) + (a22)) = sqrt(3 + 9) = sqrt(12) = 2sqrt(3)

and I'm not sure where to do on the projV(v3) question