i am trying to figure these out but my answer are marked wrong.

my teacher wont explain it to me.

according to my textbook theprojvu= [ (u dot v)/(v dot v) ] times v

consider the vectors u and v shown below

a) sketchprojuv

this would be the projection of v onto u

my answer was the red vector below

b) sketch u-projvu

i put this as the answer and the teacher said that it wasn't completely wrong but there's something missing

c) determine the exact value of (u-projvu) dotted with v. show work.

i have no idea what to do here. i know that the projection of u onto v = [ (u dot v)/(v dot v) ] times v

but i dont know what to do after that