Originally Posted by

**Alphecca** ...

As in the title; if you have two circles, how do you define the two tangents which are common to both?

...

I know i can draw out the circles and simply draw both tangents of the circles with a ruler and measure it like that. But i need something i can put into excel or a formula i can show will work **for any 2 circles of the same size** give the common tangents.

I think that’s everything. Both circles are the same size but can be anywhere relative to each other. I know the tangents have a common link that is the heading out of one circle will equal the reciprocal heading of the second circle.

Thanks in advance

Alphecca