There are examples everywhere ... but possibly the most easily recognisable is the right angle. A right angle is exactly ¼ of a full 360 degree turn. When two straight lines intersect each ...

For a right-angled triangle ... ¹ function takes the answer to adjacent ÷ hypotenuse (in this example, 16/32), and gives the angle Ɵ. To find Ɵ, calculate cos⁻¹ (16/32).