_ATAN2

The _ATAN2 function returns the radian angle between the positive x-axis of a plane and the point given by the coordinates (x, y) on it.

Syntax

angle! = _ATAN2( y, x)

Parameters

• y is the vertical axis position(row).
• x is the horizontal axis position(column).

Description

• The DOUBLE radian angle returned is positive for upper row values where y > 0.
• The DOUBLE radian angle returned is negative for lower row values where y < 0.
• _ATAN2(y, x) = ATN(y / x) when x > 0
• _ATAN2(y, x) = ATN(y / x) + _PI when x < 0 and y >= 0
• _ATAN2(y, x) = ATN(y / x) - _PI when x < 0 and y < 0
• _ATAN2(y' x) = _PI / 2 when x = 0 and y > 0
• _ATAN2(y, x) = -_PI / 2 when x = 0 and y < 0
• _ATAN2(0, 0) is undefined and the function returns 0 instead of an error.

Errors

• Note: With ATN(y / x), x can never be 0! That would create a Division by Zero error 11.

See also

• ATN (arctangent)
• _PI (QB64 constant value)
• Mathematical Operations

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