Calc 3: Proof of coplanar vectors

[Aerith's Knight]

I don't think you can, seeing as we are calculating the volume of a parrallellapiped, you can't make those factors dependant on each other. If instead t or u you would take 3(or any real number), the volume would still be 0.

to put it simple, the statement sPA + tPB + uPB = 0 only says that whatever the sizes of the vectors are, if the angle of PA is 0, then the volume is zero.