Why the familiar equal sign is a gateway into math’s—and humanity’s—most profound questions      "Eugenia Cheng has opened up my mind to the wondrous world of pure mathematics in a way that I never thought was possible." ―Willow Smith, singer and actress      A New Scientist Best Book of the Year   Math is famous for its equations: 1 + 1 = 2, a^2 + b^2 = c^2, or y = mx + b. It can seem like that’s all mathematics is: following steps to show that what’s on one side of an equation is the same as what’s on the other.      In Unequal, Eugenia Cheng shows that’s just part of the story, and the boring part to boot. Mathematics is a world of shapes, symmetries, and logical ideas. And in that world, the boundary between things being equal and unequal is a gray area, or perhaps a rainbow of beautiful, vibrant, subtly nuanced color.      As Unequal shows, once you go over that rainbow, almost everything can be considered equal and unequal at the same time, whether it’s shapes (seen from the right perspective, a circle is the same as an ellipse), words (synonyms), or people—even numbers! That’s because mathematics isn’t a series of rules, facts, or answers. It’s an invitation to a more powerful way of thinking.