http://i.stack.imgur.com/taL3F.jpg
b - proja(b) gives a vector that is parallel to the given line, right?
can you draw a picture or something, because I am kinda lost.
http://i.stack.imgur.com/taL3F.jpg
b - proja(b) gives a vector that is parallel to the given line, right?
can you draw a picture or something, because I am kinda lost.
You can find a good explanation in any calculus textbook. Use the parametric equation of a line.
Hint: When two lines are perpendicular, their dot product is zero.
Is there a value of $t$ that gives $\vec b - {\text{pro}}{{\text{j}}_{\vec a}}\vec b$?