Re: Question about Calculus on the TI-85
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"Chris Roth" <74763,45@compuserve.com> wrote:
>Is there a way to solve the derivative of a function in terms of x?
>Instead of using
>NDer (x^2,x,3) the TI gives you a value I think it gives you 6; I want it
>to give me f(3)=2x^1.
>Any help would be appreciated
I don't think that's possible. If you evaluate a derivative for a
certain x-value, you're going to get the corresponding y-value back
out. For example, the deriv of x^2 as you have above is 2x. Sticking
the 3 in there will evaluate the derivative (which is 2x) for 3, thus
spitting out 2(3) or 6. What you want is f'(x), which is the straight
derivative of the function. The 85 cannot do this using nder() right
out, and I doubt there's a calculator anywhere that can (if there is,
i'm buying it :P). What you can do is use graphs to check if your
derivative is right. Go into [graph],[y=]. In y1 put your original
function:
y1=x^2
in y2 put the nder() command with the original function. ie:
y2=nDer(x^2,x,x)
this will evaluate it for x. in y3, put in what you got for the
derivative.
y3=2x
then graph. If the last 2 lines show up the same, your deriv work was
right. I hope this made some sense..
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