An Accurate Value for Pi Is 4 Times the Arctangent of 1 (31659)




This article was previously published under Q31659

SUMMARY

An accurate value for Pi can be calculated from the ATN (arctangent) function in Microsoft BASIC as follows: 
   PI# = 4# * ATN(1#)
   PRINT PI#
The arctangent of 1, multiplied by 4, is equal to Pi.

MORE INFORMATION

Pi is equal to a circle's circumference divided by its diameter.

In Microsoft BASIC, ATN(x#) returns the arctangent of x#, where x# is a unitless number. The result returned by the ATN(x#) function is in the range -pi/2 to +pi/2 radians.

The above formula used to obtain pi applies to any product that supports the arctangent function, including the following products:

  1. Microsoft QuickBasic Versions 1.00, 1.00a, 1.00b for Apple Macintosh
  2. Microsoft BASIC Interpreter 2.x, 3.00 for the Apple Macintosh
  3. Microsoft QuickBASIC Compiler Versions 1.00, 1.01, 1.02, 2.00, 2.01, 3.00, 4.00, and 4.00b for the IBM PC
  4. Microsoft BASIC Compiler Version 5.35 and 5.36 for MS-DOS
  5. Microsoft BASIC Compiler Version 6.00 and 6.00b for MS OS/2 and MS-DOS
  6. Microsoft BASIC Professional Development System (PDS) Versions 7.00 and 7.10 for MS-DOS and MS OS/2
  7. Microsoft GW-BASIC Interpreter Versions 3.20, 3.22, and 3.23 for MS-DOS.
Modification Type: Minor Last Reviewed: 1/8/2003
Keywords: KB31659
©2002 Microsoft Corporation. All rights reserved.