Arctan, also known as inverse tangent, is a mathematical function that returns the angle whose tangent is a given number. There are several synonyms for arctan, including atan, tan^-1, and arc tangent. atan, short for arctan, is commonly used in programming languages while tan^-1 is used in mathematical notation to represent the inverse tangent function. Additionally, arc tangent is a more descriptive synonym that highlights the fact that the function returns an angle measured in radians. Whether you use arctan, atan, tan^-1, or arc tangent, the function remains the same and can be a useful tool in solving trigonometric equations.