Question

let A=(2,-1,1),B=(1,2,-1),C=(1,1,-2). A vector in the plane of B&C whose projection on A is of magnitude (2/3)^(1/2) is?
a) (2,3,-3)
b) (2,3,3)
c) (-2,-1,5)
d) (2,1,5)

Answer 1

i take it ABC are vectors to start with?

Answer 2

you could define the plane to make sure that each option is a vector in the plane, or assuming that they are ... revert to a projection setup