How to find the angle for a given point in a circle

Use the "inverse" trig-function keys on your calculator...?

Are we talking about a coordinate point on a circle centered on the origin (0,0)?

If so, then the angle represented by the one formed between a line drawn from the point to the origin with the x-axis is represented by:
\(\displaystyle \theta = tan^{-1}(\frac{y}{x})\)

From PM said:

Assume that u know the radius, x,y point. how do u find the angle to the point x,y from the center of the circle. Center is at (0,0).

Click to expand...

Ok. What we're going to do is make a triangle inside the circle.

So you have your circle, with point (X,Y) and radius r.

Put this point on a graph, and the distance from the center (0,0) to (X,Y) is r. This is your hypotenuse of the triangle.

The distance X is your length, and your height Y is the height of your triangle.

\(\displaystyle tan^{-1}(Y/X) = \theta\)