$ZARCCOS

Inverse (arc) cosine function.

Synopsis

$ZARCCOS(n)

Parameters

n	Signed decimal number.

Description

$ZARCCOS returns the trigonometric inverse (arc) cosine of n. The result is given in radians (to 18 decimal places).

Parameters

Signed decimal number ranging from 1 to -1 (inclusive). It can be specified as a value, a variable, or an expression. Numbers outside the range return an <ILLEGAL VALUE> error.

The following are arc cosine values returned by $ZARCCOS:

1	returns 0
0	returns 1.570796326794896619
-1	returns pi (3.141592653589793238)

Example

The following example permits you to compare the arc cosine and the arc sine of a number:

   READ "Input a number: ",num
   IF num>1 { WRITE !,"ILLEGAL VALUE: number too big" }
   ELSEIF num<-1 { WRITE !,"ILLEGAL VALUE: number too small" }
   ELSE { 
         WRITE !,"the arc cosine is: ",$ZARCCOS(num)
         WRITE !,"the arc sine is: ",$ZARCSIN(num)
        }
   QUIT