Students learn all kinds of facts about the American Revolution, Ancient Egypt, and World War II, but what do they learn about the history of math?Did you know that before the negative sign was invented, the ancient Chinese wrote positive values in black ink and negative values in red ink? Or that the 7th century Indian mathematician Brahmagupta had a list of rules about "debts" and "fortunes" that we now teach to our students in a unit about integers?Imagine what else your students will learn a