Cosine and Sine Ratio: Understanding cos/sin in Trigonometry

The cosine of an angle is equal to the ratio of the length of the adjacent side to the length of the hypotenuse in a right triangle. It is abbreviated as cos.

The sine of an angle is equal to the ratio of the length of the opposite side to the length of the hypotenuse in a right triangle. It is abbreviated as sin.

Therefore, cos/sin is equal to (length of adjacent side / length of hypotenuse) divided by (length of opposite side / length of hypotenuse), which simplifies to the ratio of the adjacent side to the opposite side:

cos/sin = adjacent side / opposite side