ELI5: Explain Like I'm 5

Rotation of axes

Imagine you are sitting in a room with a big ruler on the floor. The ruler goes from one wall to the other and has numbers on it from 1 to 10, going left to right. Now imagine someone comes in and rotates the ruler so that the 1 is now pointing towards the ceiling, and the 10 is pointing towards the floor. This is like a rotation of axes.

When we talk about rotation of axes in math, we are usually talking about rotating the coordinate system that we use to describe points in the plane. Instead of using the traditional x and y axes, we might use axes that are at an angle to those. This means that the coordinates (x, y) of a point might change when we rotate the axes.

For example, imagine a point at (2, 3) in the traditional x and y coordinate system. If we rotate the axes by 45 degrees, the new x and y axes will look different, but we can still find the new coordinates for our point. It turns out that the new coordinates will be about (2.12, 0.71), which means the point has moved off the traditional axes and is closer to the new x axis than the new y axis.

Rotating the axes can be useful because it can make some equations easier to work with. For example, if we have an equation that looks like y = x^2 in the traditional x and y coordinate system, it might be hard to graph it exactly. But if we rotate the axes, we might end up with an equation like y' = x'^2, which is much easier to graph because it only involves one variable.

Overall, rotation of axes is just like rotating a ruler in a room, but we are doing it to the coordinate system we use in math. It can help us solve problems and make things easier to understand.
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