The angle of rotation, is the calculation of how many degrees a shape or an object should be turned if it needs to look the same as its original position. For example, for a hexagon with 6 sides, on turning the shape to a degree of 60 degrees, the object turns its position as well as it looks the same as its original or previous position. Hence for a hexagon, the angle of rotation is 60 degrees. This online calculator is used to find the angle of rotation using the order of rotation.
An object rotated 4 times (order of rotation) to look like the same, will have an order of rotation as
a = 360 / 4
a = 90 degrees.