The term "SIN ratio" usually refers to the sine ratio, which is commonly used in trigonometry. In the context of a right triangle, the sine of an angle (usually denoted as sin(θ)) is a ratio that compares the length of the side opposite the angle to the length of the hypotenuse. The formula for the sine ratio is:
\[ \text{sin(θ)} = \frac{\text{Opposite side}}{\text{Hypotenuse}} \]
If you are dealing with different contexts, "SIN" could stand for something else, but in a typical trigonometric scenario, it's related to finding the sine ratio of an angle in a right triangle. If you meant something else by "SIN ratio," please provide more context!