Q69164: BASIC Uses Radians, Not Degrees, for Trigonometric Functions

Article: Q69164
Product(s): See article
Version(s): 1.00 1.01 1.02 2.00 2.01 3.00 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | B_BASICCOM B_GWBasicI B_BasicInt B_MQuickB | mspl13_basic
Last Modified: 14-FEB-1991

You must pass angle measurements in radians (not degrees) to BASIC's
trigonometric functions (SIN, COS, and TAN).

All versions of Microsoft BASIC require radians for the built-in
trigonometric functions (SIN, COS, TAN). Therefore, the value returned
from BASIC's SINe, COSine, and TANgent will be different than your
calculator's value, unless your calculator is using radians.

To convert degrees to radians, multiply the degrees by pi/180, where
pi equals 3.14159265359.

This information applies to the following BASIC versions:

1. Microsoft QuickBASIC versions 1.00, 1.00a, and 1.00b for Apple
   Macintosh.

2. Microsoft BASIC Compiler version 1.00 for Apple Macintosh.

3. Microsoft BASIC Interpreter versions 1.00, 1.01, 2.00, 2.10, and
   3.00 for Apple Macintosh.

4. Microsoft QuickBASIC versions 1.00, 1.01, 1.02, 2.00, 2.01, 3.00,
   4.00, 4.00b, and 4.50 for MS-DOS.

5. Microsoft BASIC Compiler versions 5.35 and 5.36 for MS-DOS.

6. Microsoft BASIC Compiler versions 6.00 and 6.00b for MS-DOS and
   MS OS/2.

7. Microsoft BASIC Professional Development System (PDS) versions 7.00
   and 7.10 for MS-DOS and MS OS/2.

8. Microsoft GW-BASIC Interpreter versions 3.20, 3.22, and 3.23 for
   MS-DOS.

Code Example
------------

'Radians = degrees * PI / 180
PI = 3.141593
X = 45
' The following prints .8509035, which is the SIN of 45 radians,
' which may not be what you wanted:
PRINT SIN(X)

' Now, convert X to radians before passing to the SIN function:
PRINT SIN(X * PI / 180)  'This gives .7071068 as the SIN of 45 degrees

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