在数学中，反三角函数是三角函数的反函数。

符号等常用于等。但是这种符号有时在和之间易造成混淆。

在编程中，函数arcsin, arccos, arctan通常叫做asin, acos, atan。很多编程语言提供两自变量atan2函数，它计算给定y和x的y/x的反正切，但是值域为。

在笛卡尔平面上f(x) = arcsin(x)(红)和f(x) = arccos(x)(绿)函数的常用主值的图像。

在笛卡尔平面上f(x) = arctan(x)(红)和f(x) = arccot(x)(绿)函数的常用主值的图像。

In mathematics, the inverse trigonometric functions (occasionally called cyclometric functions) are the inverse functions of the trigonometric functions (with suitably restricted domains). Specifically, they are the inverses of the sine, cosine, tangent, cotangent, secant, and cosecant functions. They are used to obtain an angle from any of the angle's trigonometric ratios. Inverse trigonometric functions are widely used in engineering, navigation, physics, and geometry.