# What does capital A mean in vector field notation?

This might be a dumb question but I am stuck halfway through an assignment where I am supposed to draw a bunch of vector fields because I don't understand an element of the notation.

The equation that is causing me trouble is the one below, describing a vector field in the plane, not including (0,0).

$$\textbf{v}= \frac{-Ay}{r^2}\textbf{i}+\frac{Ax}{r^2}\textbf{j}; r^2=x^2+y^2$$

The assignment does not include any addition on the capital A, so I assume that it has some conventional use that I am not familiar with?

• It looks like an arbitrary constant. Feb 18, 2021 at 13:04
• it appears to just be a scalar constant.
– lulu
Feb 18, 2021 at 13:04
• People may have trouble understanding the question (or may simply not try) due to the notation. To fix this, start here: math.stackexchange.com/help/notation Feb 18, 2021 at 13:05
• Could it be $A_y$ and $A_x$, the components of a vector $A$?
– MasB
Feb 18, 2021 at 13:05
• This is the type of question you should be asking whoever gave you that assignment. A bunch of strangers guessing could hardly offer you a sensible answer Feb 18, 2021 at 13:15

If nothing else is said about it, I would assume $$A$$ is meant to be an arbitrary real number. For the drawing, I would assume $$A > 0,$$ since for $$A=0$$ you get a zero vector field and for $$A < 0$$ all the vectors will reverse direction.