Tan is generally right. In Rt△ABC (right triangle), ∠C = 90, AB is the opposite side C of ∠ C, BC is the opposite side A of ∠A, AC is the opposite side B of ∠B, and the tangent function is tanB=b/a, that is, tanB=AC/BC.

Brief introduction of trigonometric function

Trigonometric function is one of the basic elementary functions. It is an independent variable with an angle, and the coordinates of the intersection point between the terminal edge of any angle and the unit circle corresponding to the angle or its ratio are dependent variables.

Trigonometric function plays an important role in studying the properties of geometric shapes such as triangles and circles, and is also a basic mathematical tool for studying periodic phenomena. In mathematical analysis, trigonometric functions are also defined as infinite series or specific differential equations.

Let α be an arbitrary angle and the values of the same trigonometric function with the same terminal angle are equal: sin (2kπ+α) = sinα (k ∈ z); cos(2kπ+α)= cosα(k∈Z)； tan(2kπ+α)= tanα(k∈Z)； cot(2kπ+α)=cotα(k∈Z).