atan2 has parameters swapped

New Contributor

atan2(x,y) is returning the value of atan2(y,x).

for example, if you put this in an Excel cell you should get 30 but get 60.

=degrees(atan2(sin(radians(30)), cos(radians(30)))


2 Replies
actually no I think it is correct. Remember that Sin is opposite over hyp so essentially the y coordinate and cos is adj over hyp so essentially x component so your equation is actually giving y,x and returning 60. I can draw it out if you like.

@mtarler So, what has thrown me is I expect, in spite of the argument names, for the function to take atan2(opposite, adjacent) since the tangent is opposite over adjacent. But, the name x does imply the adjacent, so I concede. Code libraries I have worked with are of the form arc2(opposite, adjacent) so that is what I was expecting. Python for example has atan2(y,x). A\This is a case of what you expect to see keeping you from seeing what is actually in the documentation.