ELI5: Explain Like I'm 5

Polar sine

Alright kiddo, let's talk about polar sine!

You know how when you draw circles, you have a center point called the origin, and then there's a line going through it that's called the x-axis? Polar coordinates are a different way of describing where points are on that circle, instead of using the x-axis and the y-axis.

Polar coordinates use two numbers instead, called r and θ. R tells you how far away the point is from the origin, and θ tells you what angle it is from the positive x-axis.

Now, sine is a math function that you use to find the opposite side of a right triangle when you know the angle and one of the other two side lengths. But what does that have to do with polar coordinates?

It turns out that you can also use sine to describe the shape of a circle using polar coordinates. Instead of thinking of it as just a series of x, y points, you can think of it as a wave that goes around and around the origin, like a spinning top.

This wave is called polar sine, or sometimes just sine of the angle. You can use it to describe all sorts of things that have circular or spiral shapes, like sound waves, water ripples, and even some types of galaxies!