Level 00 · Warm-up math
Complex numbers without fear
Numbers that point in any direction, and how they let chances cancel out.
Lesson 4 of 5 about 11 min
Numbers that sounded impossible
A few hundred years ago, many mathematicians said negative numbers were nonsense. How can you have less than nothing? Today you see them everywhere: −5 °C on a cold morning, or a bank balance below zero.
Complex numbers are the same story. They sound impossible, right up until you see a picture of them. So let's start with a picture of something you already know.
On a number line, multiplying by −1 turns a number around: 3 becomes −3. Here's a new way to see that. Multiplying by −1 is a half turn.
3
GoalMultiply by −1 twice.