Inverse trig functions are mathematical functions that are the inverse of the trigonometric functions. The three most common inverse trig functions are arctan, arcsin, and arccosine. Arctan is an abbreviation for the inverse tangent function, which is the inverse of the tangent function. Arcsin is an abbreviation for the inverse sine function, which is the inverse of the sine function. Arccosine is an abbreviation for the inverse cosine function, which is the inverse of the cosine function. All three of these inverse trig functions are used to solve equations involving trigonometric functions.