# ATAN()

### ATAN()

Arcus tangent of the argument

Syntax

`      ACOS( nTangent ) -> nRadiant`

Arguments

<nTangent> the tangent of an angle

Returns

<nRadiant> the angle whose tangent is <nTangent>

Description

The function ATAN() is the inverse function of TAN(). It takes a tangent value and returns the smallest(!) angle whose tangent equals to the argument. The return value is given in radiants between -PI()/2 and PI()/2 (full angle equals 2*Pi – see DTOR() if you need to convert it into degress).

Examples

```      ? atan( 0.0 ) // --> 0.0
? atan( 0.5 ) // --> 0.4636...```

Tests

```      atan( 0.0 ) == 0.0
atan( 1.0 ) == PI() / 4
atan( 0.0 ) == 0.0 // and not PI(), although tan( PI() ) == 0.0 !```

Compliance

ATAN() is compatible with CT3’s ATAN().

Platforms

All

Files

Source is trig.c, library is libct.

Seealso

SIN(), COS(), TAN(), COT(), ASIN(), ACOS(), ATAN(), SINH(), COSH(), TANH(), RTOD(), DTOR(), PI()

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