Assume that a formula for b hat(or y hat) using normal equation is already derivated.
t = ||y|| * cos theta
t / ||u|| = Indicating how many times the vector u must be multiplied to make the vector y hat. = scalar for making u to y hat
How does the solution always exists in normal equation?
Four fundamental subspaces of linear algebra
Why are the vectors always linearly independent, when an arbitrary set of vectors is orthogonal? (if the vectors are not zero vector.)