Sin, cos and tan are used in trigonometry to express the ratio of two sides of a triangle. The number is influenced by the angles. The 3 sides can be called:
1. adjacent: the side that near the angle
2. hypotenuse: the diagonal line
3. opposite side: the side that doesn't touch the angle.
Sin is the ratio of opposite side with the hypotenuse.
Cos is the ratio of adjacent side with the hypotenuse
Tan is the ratio of opposite side with the adjacent side. It also called ratio of sin with cos.
If put into equations it will be:
sin= opposite/ hypotenuse
cos= adjacent/hypotenuse
tan= sin/cos= opposite/adjacent