ATN

The ATN or arctangent function returns the angle in radians of a numerical tangent value.

Syntax

radianAngle = ATN(tangent!)

Parameters

• The return is the tangent!'s angle in radians.
• tangent! SINGLE or DOUBLE values are used by the function. EX:Pi = 4 * ATN(1)

Description

• To convert from radians to degrees, multiply radians * (180 / π).
• The tangent value would be equal to the tangent value of an angle. Ex: TAN(ATN(1)) = 1
• The function return value is between -π / 2 and π / 2.

Examples

Example 1: When the TANgent value equals 1, the line is drawn at a 45 degree angle (.7853982 radians) where SIN / COS = 1.

SCREEN 12 x = 100 * COS(ATN(1)) y = 100 * SIN(ATN(1)) LINE (200, 200)-(200 + x, 200 + y)

Example 2: ATN can be used to define π in SINGLE or DOUBLE precision. The calculation cannot be used as a CONSTant.

Pi = 4 * ATN(1) 'SINGLE precision Pi# = 4 * ATN(1#) 'DOUBLE precision PRINT Pi, Pi#

Note: You can use QB64's native _PI function.

Example 3: Finds the angle from the center point to the mouse pointer.

SCREEN _NEWIMAGE(640, 480, 32) x1! = 320 y1! = 240 DO PRESET (x1!, y1!), _RGB(255, 255, 255) dummy% = _MOUSEINPUT x2! = _MOUSEX y2! = _MOUSEY LINE (x1, y1)-(x2, y2), _RGB(255, 0, 0) LOCATE 1, 1: PRINT getangle(x1!, y1!, x2!, y2!) _DISPLAY _LIMIT 200 CLS LOOP UNTIL INKEY$ <> "" END FUNCTION getangle# (x1#, y1#, x2#, y2#) 'returns 0-359.99... IF y2# = y1# THEN IF x1# = x2# THEN EXIT FUNCTION IF x2# > x1# THEN getangle# = 90 ELSE getangle# = 270 EXIT FUNCTION END IF IF x2# = x1# THEN IF y2# > y1# THEN getangle# = 180 EXIT FUNCTION END IF IF y2# < y1# THEN IF x2# > x1# THEN getangle# = ATN((x2# - x1#) / (y2# - y1#)) * -57.2957795131 ELSE getangle# = ATN((x2# - x1#) / (y2# - y1#)) * -57.2957795131 + 360 END IF ELSE getangle# = ATN((x2# - x1#) / (y2# - y1#)) * -57.2957795131 + 180 END IF END FUNCTION

Function by Galleon

See also

• _PI (QB64 function)
• _ATAN2 ((QB64 function)
• TAN (tangent function)
• SIN, COS
• Mathematical Operations
• Derived Mathematical Functions

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