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42 lines
1.5 KiB
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42 lines
1.5 KiB
Plaintext
{{QBDLDATE:05-20-2022}}
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{{QBDLTIME:23:06:30}}
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{{DISPLAYTITLE:_ATAN2}}
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The [[_ATAN2]] function returns the radian angle between the positive x-axis of a plane and the point given by the coordinates (x, y).
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{{PageSyntax}}
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: {{Parameter|angle!}} = [[_ATAN2]]({{Parameter|y}}, {{Parameter|x}})
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{{Parameters}}
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* {{Parameter|y}} is the vertical axis position (row) as a positive, zero or negative floating point value.
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* {{Parameter|x}} is the horizontal axis position (column) as a positive, zero or negative floating point value.
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{{PageDescription}}
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* The [[DOUBLE]] radian angle returned is '''positive''' for upper row values where y > 0.
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::* _ATAN2(y, x) = [[ATN]](y# / x#) when x > 0
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::* _ATAN2(y, x) = [[ATN]](y# / x#) + [[_PI]] when x < 0
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::* _ATAN2(y, x) = [[_PI]] / 2 when x = 0
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* The [[DOUBLE]] radian angle returned is 0 when x > 0 and [[_PI]] when x < 0 where y = 0
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* The [[DOUBLE]] radian angle returned is '''negative''' for lower row values where y < 0.
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::* _ATAN2(y, x) = [[ATN]](y# / x#) when x > 0
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::* _ATAN2(y, x) = [[ATN]](y# / x#) - [[_PI]] when x < 0
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::* _ATAN2(y, x) = -[[_PI]] / 2 when x = 0
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* _ATAN2(0, 0) is undefined and the function returns 0 instead of a division error.
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{{PageErrors}}
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* With [[ATN]](y / x), x can never be 0 as that would create a Division by Zero [[ERROR Codes|error]] 11 or #IND.
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{{PageSeeAlso}}
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* [[ATN]] {{text|(arctangent)}}
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* [[_PI]] {{text|(QB64 function)}}
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* [[Mathematical Operations]]
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* [https://en.wikipedia.org/wiki/Atan2 Atan2 reference]
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{{PageNavigation}}
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