 Now we can look at velocity in two dimensions. Again, when we had velocity in one dimension, it was the symbol vector v, and it could be a horizontal velocity or a vertical velocity. In either case, it was a vector because it mattered which direction you were going, and it had standard dimensions of length per time with a standard unit of meters per second in the metric system. Well, in two dimensions, those x and y velocities become components of a single velocity, and they become vx and vy. The magnitude, though, is still just v, and I still have a direction of theta. Using our standard vector notation, the full vector, vector v, is vx in the i-hat direction plus vy in the j-hat direction. The magnitude still follows the Pythagorean theorem, but now it's v that we're finding the magnitude of, and it's vx squared plus vy squared. And if I measure my direction, again, relative to the positive x-axis, then my angle theta is the inverse cosine of vy over vx using our normal trick. Now graphically, we still have the same sort of triangle we had for position, but we recognize that this vector v is not the position vector, it's the velocity vector. But it still has components of vx and vy, whether you want to draw that as a triangle or the projections of the velocity out onto the x and y-axis. And that introduces how we're going to show velocity in two dimensions. We'll talk about the equations later.