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ATAN2

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Returns the arctangent, or inverse tangent, of the specified x- and y-coordinates. The arctangent is the angle from the x-axis to a line containing the origin (0, 0) and a point with coordinates (x_num, y_num). The angle is given in radians between -pi and pi, excluding -pi.

Syntax

ATAN2 ( x_num , y_num )

X_num is the x-coordinate of the point.

Y_num is the y-coordinate of the point.

Remarks

  • A positive result represents a counterclockwise angle from the x-axis; a negative result represents a clockwise angle.

  • ATAN2(a,b) equals ATAN(b/a), except that a can equal 0 in ATAN2.

  • If both x_num and y_num are 0, ATAN2 returns the #DIV/0! error value.

  • To express the arctangent in degrees, multiply the result by 180/PI( ) or use the DEGREES function.

Example

Formula

Description (Result)

=ATAN2(1, 1)

Arctangent of the point 1,1 in radians, pi/4 (0.785398)

=ATAN2(-1, -1)

Arctangent of the point -1,-1 in radians, -3*pi/4 (-2.35619)

=ATAN2(-1, -1)*180/PI()

Arctangent of the point 1,1 in degrees (-135)

=DEGREES(ATAN2(-1, -1))

Arctangent of the point 1,1 in degrees (-135)

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