Finding true angle on a plot?

[spacely]

Hi,

Maybe this isn't an excel question, but perhaps you can help?

How do we determine the angle between 2 plots (of a line), where the x-axis and y-axis has completely different Units and Scale? The arctan function requires a unitless argument to get a real angle, but if you take rise/run on a plot with completely different axis units, it won't be unitless.

Maybe someone worked this out already?

 

[Rick Rothstein]

Hi,

Maybe this isn't an excel question, but perhaps you can help?

How do we determine the angle between 2 plots (of a line), where the x-axis and y-axis has completely different Units and Scale? The arctan function requires a unitless argument to get a real angle, but if you take rise/run on a plot with completely different axis units, it won't be unitless.

Maybe someone worked this out already?

The ArcTan function returns a unitless value, but the two numbers you divide are not unitless, they just need to have the same unit for both. So, if you have two different units, you need to convert the number for one unit to its equivalent value in the other unit and then divide those two numbers. You did not tell us what the two units you have are, so I cannot give you any more detail than what I did above.

 

[spacely]

Yes, and now I realize that the conversion used for one of the lines better be the same as used to convert ALL the lines with which we compare angles on that same plot. A different "conversion" per line is wrong, if they share the same plot

Thanks.