Tan-1

Tan-1, TAN-1, tan-1, or tan&minus;1 may refer to:

Because of ambiguity, the notation arctan(x) or (tan(x))&minus;1, is recommended.
 * tan&minus;1y = tan&minus;1(x), sometimes interpreted as arctan(x) or arctangent of x, the compositional inverse of the trigonometric function tangent (see below for ambiguity)
 * tan&minus;1x = tan&minus;1(x),  interpreted as (tan(x))&minus;1 = $1⁄tan(x)$ = cot(x) or cotangent of x, the multiplicative inverse (or reciprocal) of the trigonometric function tangent (see above for ambiguity)
 * tan x&minus;1, sometimes interpreted as tan(x&minus;1) = tan($1⁄x$), the tangent of the multiplicative inverse (or reciprocal) of x (see below for ambiguity)
 * tan x&minus;1, sometimes interpreted as (tan(x))&minus;1 = $1⁄tan(x)$ = cot(x) or cotangent of x, the multiplicative inverse (or reciprocal) of the trigonometric function tangent (see above for ambiguity)