# Math Help - Projections

1. ## Projections

If a b than a ↓ b = (a*b/(|b|^2))b and b ↓ a = (b*a/(|a|^2))a correct? If not, why will b ↓ a will still be (b*a/(|a|^2)) but with a multiple of b at the end? That is why my book is saying in the back. That it is still vector b as compared to vector a.

2. Originally Posted by Barthayn
If a b than a ↓ b = (a*b/(|b|^2))b and b ↓ a = (b*a/(|a|^2))a correct? If not, why will b ↓ a will still be (b*a/(|a|^2)) but with a multiple of b at the end? That is why my book is saying in the back. That it is still vector b as compared to vector a.
It appears that you are talking about projections
$a \downarrow b = \text{proj}_b a = \frac{{a \cdot b}}{{b \cdot b}}b$.