# Velocity vector

1. Sep 2, 2004

### CellCoree

If $$r^{\rightarrow} = bt^2i+ct^3j$$, where $$b$$ and $$c$$ are positive constants, when does the velocity vector make an angle of $$45.0^o$$ with the x- and y-axes?

i & j are vectors.

i have no clue on how to start it, can anyone give me a hint?

2. Sep 2, 2004

### Tide

There are several approaches you could take. Here's one: