Dumb piloting question
01-14-2017, 10:41 PM
Post: #2
 Eddie W. Shore Senior Member Posts: 1,534 Joined: Dec 2013
RE: Dumb piloting question
(01-14-2017 07:33 PM)lrdheat Wrote:  How do I enter a d/dX function such as d(sin X)/dX into the graphing app to plot? I keep getting a plot where f(X)=0 for all X.

This is not a dumb plotting question at all. I thought using the Function app command SLOPE would work:

SLOPE( f(X), X ) but all zeroes are plotted. That shouldn't be happening.

A way to plot the derivative, but two function slots will be needed:

F1(X) = f(x), unchecked (or checked if you want)
F2(X) = ((F1(X) + dx) - (F(X) - dx))/dx (checked)

dx is small, like dx = 0.01 or 0.001. You can make dx smaller but I find using the definition of the derivative for simple problems, 0.01 and 0.001 work well.

Example:
F1(X) = 2*X^2
F2(X) = ((F1(X) + 0.01) - (F1(X) - 0.01))/0.01

There are other derivative numerical formulas if needed.

I hope this gets addressed for the next Prime update.

Eddie
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 Messages In This Thread Dumb piloting question - lrdheat - 01-14-2017, 07:33 PM RE: Dumb piloting question - Eddie W. Shore - 01-14-2017 10:41 PM RE: Dumb piloting question - Han - 01-14-2017, 10:45 PM RE: Dumb piloting question - cyrille de brĂ©bisson - 01-16-2017, 06:24 AM RE: Dumb piloting question - lrdheat - 01-16-2017, 03:33 PM RE: Dumb piloting question - lrdheat - 01-20-2017, 12:03 AM RE: Dumb piloting question - Geoff Quickfall - 01-20-2017, 05:56 AM RE: Dumb piloting question - d b - 01-20-2017, 07:30 AM RE: Dumb piloting question - StephenG1CMZ - 01-20-2017, 06:08 PM RE: Dumb piloting question - Geoff Quickfall - 01-20-2017, 07:55 AM RE: Dumb piloting question - lrdheat - 01-20-2017, 09:57 PM