Instructions

In this problem all we know is the radii of both circles and the distance between them, yet

we have to arrive at the tangent points.

Figure 13

Here is the real problem. The seemingly obvious way of solving this problem would be to

solve the angle that can be generated with the differences between the radii and the

distances between centers and then use this information to come up the needed points.

Wrong. Compare the two angles in Fig. 14 below. Although the error isn’t that great for

laying out sheet metal work, it’s a gigantic error for a computer to swallow, and you have

to be accurate to four places.