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## Inventor General

Valued Contributor
Posts: 58
Registered: ‎04-05-2007
Message 1 of 5 (697 Views)

# Why does Equation Curve function not work?

697 Views, 4 Replies
05-10-2012 06:54 AM

Trying to do something as simple as y=x^3 (Explicit Mode). Set xmin = 10, xmax = 20 then tried y(x) = :

1in *(x^3) -- no good

(x^3)/1 in -- no good

(x/1 in)^3 -- no good

Error is that "Equation y(x) contains errors. Expected units are length".

The point here is: Why should tpying in such a simple equation as y=x^3 be so difficult??? Can't even do (x*x*x)/1 in & make it work.

It's really great that the example shows an airfoil equation, but how about starting with the simple stuff & getting it to work right first???

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Posts: 23,684
Registered: ‎04-20-2006
Message 2 of 5 (676 Views)

# Re: Why does Equation Curve function not work?

05-10-2012 09:32 AM in reply to: marshallw

Try something like this

oops, but inches (in) as your units and of course the 25 was just a test number.

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Posts: 92
Registered: ‎09-24-2008
Message 3 of 5 (636 Views)

# Re: Why does Equation Curve function not work?

05-15-2012 05:40 AM in reply to: JDMather

marshallw,

When creating explicit equations, the units for xmin and xmax are length. So your equation is (x^3) / (1 in * 1 in) so you end up with in for the end units.

The Tutorial for equation curves uses simpler equations that what are shown in the airfoil video.

Patrick Miller
Senior Content Developer
Autodesk, Inc.

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Valued Contributor
Posts: 58
Registered: ‎04-05-2007
Message 4 of 5 (583 Views)

# Re: Why does Equation Curve function not work?

06-01-2012 01:44 PM in reply to: marshallw

Thank you Patrick & JD. I noticed that both you solutions involved dividing x^3 by 1{measurement unit}^2. I would have never thought of dividing x^3 by something squared to get the answer, which was exactly my point to Autodesk on the original post -- whay so dang complex?

Are you folks saying that I have to take into accound the units for both xmin & xmax in the equation? Is that the reason for dividing by 1{unit}^2/

Marshall

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Posts: 23,684
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Message 5 of 5 (572 Views)

# Re: Why does Equation Curve function not work?

06-01-2012 03:25 PM in reply to: marshallw

marshallw wrote:

I would have never thought of dividing x^3 by something squared to get the answer, which was exactly my point to Autodesk on the original post -- whay so dang complex?

Seems pretty logical to me - I recall learning how to handle units in HS math.

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