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## Why is a circle 360 degrees and not 400?

The ancient Babylonians used a sexagesimal numbering system, with a base of 60, rather than the decimal system we use today (with a base of 10). This is also why there are 60 minutes in an hour, and the hours and months are numbered one to 12. The suggestion that there should be 400 units for a circle has merit.

## Why do we use 360 for the size of a full turn and not some other number?

360 is an incredibly abundant number, which means that there are many factors. So it makes it easy to divide the circle into 2,3,4,5,6,8,9,10,12,… parts. By contrast, 400 gradians cannot even be divided into 3 equal whole-number parts.

## Who first divided the circle into 360?

Timocharis, Aristarchus, Aristillus, Archimedes, and Hipparchus were the first Greeks known to divide the circle in 360 degrees of 60 arc minutes.

## What are the rules for 90 degrees clockwise and counterclockwise?

90 Degree Rotation When rotating a point 90 degrees counterclockwise about the origin our point A(x,y) becomes A'(-y,x). In other words, switch x and y and make y negative.

## What is the general rule for a 270 clockwise rotation?

When we rotate a figure of 270 degree clockwise, each point of the given figure has to be changed from (x, y) to (-y, x) and graph the rotated figure.

## Is 90 degrees clockwise the same as 270 degrees counterclockwise?

Rotating 90 degrees clockwise is the same as rotating 270 degrees counterclockwise. Rotating 270 degrees counterclockwise about the origin is the same as reflecting over the line y = x and then reflecting over the x-axis.

## What is the rule for 360 degrees counterclockwise?

Clockwise rotations are denoted by negative numbers. Counterclockwise rotations are denoted by positive numbers. Note that the direction of rotation (CW or CCW) doesn’t matter for 180 and 360-degree rotations, since they will both bring you to the same spot (more on this later).

2020-08-06