*How Round is Your Circle?*. 2008, with Chris Sangwin

How do you know if a circle is really round? Or if a line is truly straight?
These may sound like simple or even trivial mathematical questions,
but to an engineer the answers can mean the difference between success and failure.
*How Round Is Your Circle?* invites you to explore many of
the same fundamental questions that working engineers deal with every day.

Using elementary geometry and trigonometry, John Bryant and Chris Sangwin illustrate
how to turn abstract mathematical models into physical tools that can solve real-life problems,
from keeping a piston aligned in its cylinder to ensuring that automotive driveshafts rotate smoothly.
They guide readers through paper-and-pencil reconstructions of mathematical problems
and even provide instructions for how to build actual physical models.
Combining problem-solving with stories from engineering history,
*How Round Is Your Circle?* reveals some of the hidden complexities in everyday things.