ATAN Function

ATAN(real-expression)

Returns the arc tangent (inverse tangent) of the given expression, in radians.

The result will always lie between -PI#/2 and PI#/2.

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Examples

PRINT ATAN(0)

Produces 0.

PRINT ATAN(1)

Produces approximately 0.785398 (π/4).

PRINT ATAN(-1)

Produces approximately -0.785398 (-π/4).

REM Validate a tangent identity
angle# = 0.3
PRINT ATAN(TAN(angle#))

Produces the original angle (within floating point accuracy).

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Notes

• Input range: any real number is valid.
• Return range: -π/2 ≤ result ≤ π/2 radians.
• To convert the result to degrees, multiply by 180 / PI.
• For quadrant-aware arc tangent with two arguments (x,y), use ATAN2.

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See also: TAN · ATAN2 · ACS · ASN