4.3 Trigonometry
When we discuss single qubits and what we can do with them in Chapter 7, “One Qubit,” we will see that many of the operations we perform are rotations, and for these, we must know how to manipulate angles. The trigonometric functions like sine and cosine are foundational tools for working with angles, and this section reviews their properties and identities. trigonometry
The Greek word trígōnon means “triangle,” and metron means “measure.”
4.3.1 The fundamental functions
Many people have heard that a circle has 360 degrees, also written 360○. Why 360? Looking around the web, you find stories about ancient Mesopotamians, Egyptians, and base 60 number systems. Whatever the reason, 360 is a convenient number because it is divisible by so many other numbers, such as 2, 3, 4, 5, 6, 8, 10, 12, 15, and so on. That is, it’s easy to work with portions...
