topic Re: iLogic difference in calculating TAN with degrees and mm in Inventor Forum

iLogic difference in calculating TAN with degrees and mm

Anonymous — Tue, 12 May 2015 09:08:12 GMT

Good morning World!

I am currently trying to make a calculation with Tangent with degrees. I get a different outcome while working mm.

For example:

Height = 1000 mm

Angle = 50 deg

X = Height / TAN(Angle) = 642,092615934331 mm

While adding another parameter, with the angle being in mm I get a different outcome.

For example:

Height = 1000 mm

Angle = 50 deg

Angle = Angle_mm

X = Height / TAN(Angle_mm) = 617,369623783555 mm

I need the TAN to work the same way as it would in mm as with degrees.

Anyone knows a solution for this, or am I doing something wrong here?

Regards,

Mark

Re: iLogic difference in calculating TAN with degrees and mm

swalton — Tue, 12 May 2015 15:31:11 GMT

For iLogic:

All trig functions use radians. You will have to convert all your angle measurements to rad before using them in a trig function. Also, trig functions require angle measures, not length measures. Tan(2 rad) works. Tan(2 mm) is wrong.

See http://help.autodesk.com/view/INVNTOR/2014/ENU/?guid=GUID-E9CF6373-3E22-4E25-9F1D-49B8602A8EC0

For parameters:

All trig functions in Inventor expect an angle unit. Angles are measured in deg, radians, grad, or steradians. Tan(deg) or Tan(rad) are valid. Tan(mm) or tan(inches) are not.

See the attached screenshot. IV returns a value for tan(inches) but it is highlighted in red to show that the units are not correct. Also, the calculated value is not the same as the tan(deg) or the tan(rad) calculations. I don't know why Inventor calculates anything when the units are wrong. I think it should throw an error and force you to fix it before you can close the parameters window.

Re-work your equation to use an angle unit for your normal trig functions and unitless values for your inverse trig functions.

Edited to show difference between ilogic and parameters.

Re: iLogic difference in calculating TAN with degrees and mm

Anonymous — Wed, 13 May 2015 07:41:49 GMT

Thanks for your reply, and clarification. It kind of makes sense now.

I tried mm because my outcome in degrees wasn't correct for some reason, and still isn't. I'll try the unitless solution now and hope it works as I'd like.

Thanks for the time to work this out 🙂

Re: iLogic difference in calculating TAN with degrees and mm

Anonymous — Wed, 13 May 2015 07:55:38 GMT

Still isn't working as intended. I mean it still does the same thing with unitless as with degrees

Basically I use parameters with both angle and length measurements, mm and degrees.

I'll show you a similair example with parameters that are a little clearer, because my language isn't English.

Slope = StairRise / Sin(Angle)

Slope = mm
StairRise = mm
Angle = deg

It's just a simple formula but it's not giving me the same outcome as it would on my calculator. I'm also working in an assembly level, linking parameters from parts to my main User Parameter in the main assembly. I don't know where it's going wrong.

I could send a screenshot but it's not going to make things any clearer since they are random names.

Re: iLogic difference in calculating TAN with degrees and mm

Anonymous — Wed, 13 May 2015 09:33:31 GMT

Okay so I found out the solution.

Apparantely Inventor calculates in Rad, EVEN when your Document Dettings are set to Deg.

Therefore my angle was calculated in Rad and not in Deg inside iLogic, which caused my problem. I just had to convert the Rad to Deg and it solved my problem.

Problem:

 Slope = SlopeIncline / Sin(Angle)

Solution:

 Slope = SlopeIncline / Sin(Angle*PI/180)

Thanks for your advice, definately helped me to figure it out.