Tan-1, TAN-1, tan-1, or tan⁻¹ may refer to:

• tan⁻¹y = tan⁻¹(x), sometimes interpreted as arctan(x) or arctangent of x, the compositional inverse of the trigonometric function tangent (see below for ambiguity)
• tan⁻¹x = tan⁻¹(x), sometimes interpreted as (tan(x))⁻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⁻¹, sometimes interpreted as tan(x⁻¹) = tan(⁠1/x⁠), the tangent of the multiplicative inverse (or reciprocal) of x (see below for ambiguity)
• tan x⁻¹, sometimes interpreted as (tan(x))⁻¹ = ⁠1/tan(x)⁠ = cot(x) or cotangent of x, the multiplicative inverse (or reciprocal) of the trigonometric function tangent (see above for ambiguity)^{[citation needed]}

Because of ambiguity, the notation arctan(x) or (tan(x))⁻¹, is recommended.

• Inverse function
• cot⁻¹ (disambiguation)
• atan2

Topics referred to by the same term

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