# $ZTAN

## Synopsis

$ZTAN(n)

### Parameter

Argument | Description |
---|---|

n | An angle in radians ranging from Pi to 2 Pi (inclusive). Other supplied numeric values are converted to a value within this range. |

## Description

$ZTAN returns the trigonometric tangent of n. The result is a signed decimal number.

$ZTAN (like all trigonometric functions) calculates its values based on pi rounded to the number of available decimal digits. Therefore, the value returned by $ZTAN($ZPI) is –.000000000000000000462644 and $ZTAN(–$ZPI) is .000000000000000000462644. For this reason you should not perform limit tests comparing these returned values to 0. $ZTAN(0) is 0.

## Parameter

### n

An angle in radians ranging from 0 to 2 Pi. It can be specified as a value, a variable, or an expression.

A non-numeric string is evaluated as 0.

## Examples

The following example permits you to compute the tangent of a number:

READ "Input a number: ",num WRITE !,"the tangent is: ",$ZTAN(num) QUIT

The following example compares the results from InterSystems IRIS fractional numbers ($DECIMAL numbers) and $DOUBLE numbers. In both cases, the tangent of 0 is exactly 0, but the tangent of pi is a negative fractional number (not exactly 0):

WRITE !,"the tangent is: ",$ZTAN(0.0) WRITE !,"the tangent is: ",$ZTAN($DOUBLE(0.0)) WRITE !,"the tangent is: ",$ZTAN($ZPI) WRITE !,"the tangent is: ",$ZTAN($DOUBLE($ZPI)) WRITE !,"the tangent is: ",$ZTAN(1.0) WRITE !,"the tangent is: ",$ZTAN($DOUBLE(1.0))