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+--- Thread: How to evaluate f'' at a specific point? (/thread-3945.html)
How to evaluate f'' at a specific point? - lrdheat - 05-22-2015 05:49 PM
Dumb question...how in home or CAS do I enter f''(3 root (x-2)) where x=some number of interest?
RE: How to evaluate f'' at a specific point? - DrD - 05-22-2015 06:46 PM
Did you try:
(x-2)^(1/3)''
or:
∂((x-2)^(1/3),x)'
RE: How to evaluate f'' at a specific point? - lrdheat - 05-22-2015 07:20 PM
In trying to get the second derivative at a specified point, I'm having difficulty in accessing the proper syntax. The template gives me d/dx. I can then get, say, ((d 3 root x-2 / dx)/dx))|x=1.99.
This returns 0 instead of 478+. What am I doing wrong?
RE: How to evaluate f'' at a specific point? - Helge Gabert - 05-22-2015 08:42 PM
I would just do
diff(diff(3ROOT(x-2),x),x) and then
Ans|x=1.99 (Ans actually has to be copied explicitly from the command line above)
returns 478.76 . . . for me.
Or do you have to do it with the d/dx template?
[You can also define f(x):=3Root(x-2), and then simply type f''(1.99) also returns 478.76 . . .]
RE: How to evaluate f'' at a specific point? - lrdheat - 05-22-2015 09:03 PM
That works (thanks!). Seems like there should be a more direct way to do this.
RE: How to evaluate f'' at a specific point? - toshk - 05-22-2015 09:50 PM
(∂(∂((x-2)^(1/3),x),x)|(x )= 1.99)
Credit: Eddie's Math and Calculator Blog series, by Edward Shore
3.24.
RE: How to evaluate f'' at a specific point? - parisse - 05-23-2015 05:49 AM
More natural syntax:
f(x):=(2-x)^(1/3);
f''(1.99)
For a large number of derivatives, for example 5, run diff(f(x),x,5)(x=1.99)
RE: How to evaluate f'' at a specific point? - lrdheat - 05-23-2015 04:11 PM
Thanks...this is what I hoped for! And when using the n root entry, negative results are produced for this equation directly as opposed to a complex number result!
RE: How to evaluate f'' at a specific point? - lrdheat - 05-23-2015 04:19 PM
Can this syntax be used in the function graphing app...the diff(f(x),x,2) form? What is the proper syntax for this?