IGRP Episode 19 Practice 1. Problem 20. Four pairwise externally tangent circles

Starting from this episode we begin applying the new material that we have learned in this course so far to problems that at first blush seem to have nothing to do with inversive geometry. However, as we shall see soon enough, there is more to mathematics than what meets the eye. In certain situations the application of inversive geometry may not only be possible but it may also lead to quite crisp and elegant proofs/computations. In this, opener, problem we look exactly at such a scenario. Yes, the Problem 20 can very well be solved using nothing more than the good old middle school "angle-chasing" technology. But that is not the point of this exercise. The point of this exercise is not to generate "the shortest" or "the simplest" proof but to get into a habit of looking at a given technical problem under different angles in order to showcase one's creativity and ingenuity, step out of the proverbial box and bring in a new tool to the rescue. And in this episode we show how can this be done.