Cot is cotangent. In a right triangle, the cotangent of an acute angle is equal to its adjacent side.

Common relations of trigonometric functions:

Square relation: sin? 0? 5a+cos？ 0? 5a= 1

Reciprocal relationship: tana = 1/cota, cota = 1/tana.

Quotient relation: tana=sina/cosa

There's another one. I don't know whether to write it down. 1+ Tan? 0? 5a = seconds? 0? 5a. 1+cot？ 0? 5a=csc？ 0? 5a

If you are a junior high school student, its role in mathematics is basically to solve triangles, and there are triangle substitution and polar coordinates in high school.