How to make two nodes located in symmetry?

[hugo.paradox]

So I wanted to make two nodes on a circle; one is on one side and the other one is on the other side. However I want them to be symmetric with respect to y-axis (vertical middle line of the circle).

 

How can I accomplish this in easiest way?

[firstdefence]

Create a rectangle to overlay the circle so the bottom line sits where you want the nodes added, the top of the rectangle must be above the top of the circle.

Removes the outer part of the rectangle. 

This will leave the nodes where the rectangle intersected the circle. 

Result.

[dutchshader]

Or drag out a guide to that position

[Move Along People]

-