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# A to Z of Excel Functions: the ATAN2 Function

9 September 2016

Welcome back to our regular A to Z of Excel Functions blog.  Today we look at the ATAN2 function.

The ATAN2 function

You see that bronzed figure on the beach and you think, maybe I should get ATAN2.  Yes, this function 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 - π and π, excluding - π.

The ATAN2 function employs the following syntax to operate:

ATAN2(x_num, y_num)

The ATAN2 has the following arguments:

• x_num: this is required and represents the x-coordinate of the point
• y_num: this is also required and represents the y-coordinate of the point.

It should be further noted that:

• A positive result represents an anti-clockwise 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.