# Thread: Finding points on circles

1. ## Finding points on circles

Hi,

Attached I have a picture of my problem. I know that every circle can be said that is surrounded by a square, but I need to know certain point on a circle. How is that possible pls?

2. Originally Posted by doobybug
Hi,

Attached I have a picture of my problem. I know that every circle can be said that is surrounded by a square, but I need to know certain point on a circle. How is that possible pls?
1. The equation of your circle is:

$\displaystyle (x-250)^2+(y-250)^2=150^2$

To calculate the coordinates of a ceratin point you must know either the x-value or the y-value of the point.

2. If you know the angle $\displaystyle \alpha$ between the given radius and the point in question then you can calculate the coordinates of the point P:

$\displaystyle x_P=250+150\cdot \cos(\alpha)$

$\displaystyle y_P=250+150\cdot \sin(\alpha)$

3. ## triangles

If the other response is too complex. Use (right) triangles and you will be able to figure it out.