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94 lines
2.2 KiB
Markdown
94 lines
2.2 KiB
Markdown
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The [ATN](ATN) or arctangent function returns the angle in radians of a numerical [TAN](TAN) value.
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## Syntax
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> radianAngle = [ATN](ATN)(tangent!)
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## Parameter(s)
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* The return is the tangent!'s angle in **radians**.
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* tangent! [SINGLE](SINGLE) or [DOUBLE](DOUBLE) values are used by the function. EX:**Pi = 4 * ATN(1)**
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## Description
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* To convert from radians to degrees, multiply radians * (180 / <20>).
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* The *tangent* value would be equal to the tangent value of an angle. Ex: **[TAN](TAN)(ATN(1)) = 1**
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* The function return value is between -<2D> / 2 and <20> / 2.
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## Example(s)
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When the [TAN](TAN)gent value equals 1, the line is drawn at a 45 degree angle (.7853982 radians) where [SIN](SIN) / [COS](COS) = 1.
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```vb
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SCREEN 12
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x = 100 * COS(ATN(1))
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y = 100 * SIN(ATN(1))
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LINE (200, 200)-(200 + x, 200 + y)
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```
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[ATN](ATN) can be used to define π in [SINGLE](SINGLE) or [DOUBLE](DOUBLE) precision. The calculation cannot be used as a [CONST](CONST)ant.
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```vb
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Pi = 4 * ATN(1) 'SINGLE precision
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Pi# = 4 * ATN(1#) 'DOUBLE precision
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PRINT Pi, Pi#
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```
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> *Note:* You can use QB64's native [_PI](_PI) function.
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Finds the angle from the center point to the mouse pointer.
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```vb
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SCREEN _NEWIMAGE(640, 480, 32)
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x1! = 320
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y1! = 240
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DO
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PRESET (x1!, y1!), _RGB(255, 255, 255)
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dummy% = _MOUSEINPUT
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x2! = _MOUSEX
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y2! = _MOUSEY
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LINE (x1, y1)-(x2, y2), _RGB(255, 0, 0)
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LOCATE 1, 1: PRINT getangle(x1!, y1!, x2!, y2!)
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_DISPLAY
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_LIMIT 200
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CLS
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LOOP UNTIL INKEY$ <> ""
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END
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FUNCTION getangle# (x1#, y1#, x2#, y2#) 'returns 0-359.99...
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IF y2# = y1# THEN
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IF x1# = x2# THEN EXIT FUNCTION
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IF x2# > x1# THEN getangle# = 90 ELSE getangle# = 270
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EXIT FUNCTION
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END IF
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IF x2# = x1# THEN
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IF y2# > y1# THEN getangle# = 180
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EXIT FUNCTION
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END IF
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IF y2# < y1# THEN
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IF x2# > x1# THEN
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getangle# = ATN((x2# - x1#) / (y2# - y1#)) * -57.2957795131
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ELSE
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getangle# = ATN((x2# - x1#) / (y2# - y1#)) * -57.2957795131 + 360
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END IF
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ELSE
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getangle# = ATN((x2# - x1#) / (y2# - y1#)) * -57.2957795131 + 180
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END IF
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END FUNCTION
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```
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## See Also
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* [_PI](_PI) (QB64 function)
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* [TAN](TAN) (tangent function)
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* [SIN](SIN), [COS](COS)
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* [Mathematical Operations](Mathematical-Operations)
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* [Mathematical Operations](Mathematical-Operations)
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