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Command Summary

Returns the inverse tangent (also called arctangent)

Command Syntax


Menu Location


  1. [2nd]
  2. [tanֿ¹]

Calculator Compatibility


Token Size

1 byte

tanֿ¹( returns the arctangent of its argument. It is the inverse of Tan(, which means that tanֿ¹(n) produces an angle θ such that tan(θ)=n.

Like tan(, the result of tanֿ¹( depends on whether the calculator is in Radian or Degree mode. However, unlike tangent, the result is in degrees or radians, not the argument. A full rotation around a circle is 2π radians, which is equal to 360°. The conversion of θ=tanֿ¹(n) from radians to degrees is θ*180/π and from degrees to radians is θ*π/180. The tanֿ¹( command also works on a list.

tanֿ¹( will always return a value between -π/2 and π/2 (or -90° and 90°).

In radians:


In degrees:



Expressions of the form tanֿ¹(y/x) are usually better recast as R►Pθ(x,y); the latter will not fail even if x should happen to be equal to zero.

Error Conditions

  • ERR:DATA TYPE is thrown if you input a complex value or a matrix.

Related Commands