How to evaluate f'' at a specific point?

05222015, 05:49 PM
Post: #1




How to evaluate f'' at a specific point?
Dumb question...how in home or CAS do I enter f''(3 root (x2)) where x=some number of interest?


05222015, 06:46 PM
Post: #2




RE: How to evaluate f'' at a specific point?
Did you try:
(x2)^(1/3)'' or: ∂((x2)^(1/3),x)' 

05222015, 07:20 PM
Post: #3




RE: How to evaluate f'' at a specific point?
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 x2 / dx)/dx))x=1.99.
This returns 0 instead of 478+. What am I doing wrong? 

05222015, 08:42 PM
(This post was last modified: 05222015 08:53 PM by Helge Gabert.)
Post: #4




RE: How to evaluate f'' at a specific point?
I would just do
diff(diff(3ROOT(x2),x),x) and then Ansx=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(x2), and then simply type f''(1.99) also returns 478.76 . . .] 

05222015, 09:03 PM
Post: #5




RE: How to evaluate f'' at a specific point?
That works (thanks!). Seems like there should be a more direct way to do this.


05222015, 09:50 PM
(This post was last modified: 05222015 09:59 PM by toshk.)
Post: #6




RE: How to evaluate f'' at a specific point?
(∂(∂((x2)^(1/3),x),x)(x )= 1.99)
Credit: Eddie's Math and Calculator Blog series, by Edward Shore 3.24. 

05232015, 05:49 AM
Post: #7




RE: How to evaluate f'' at a specific point?
More natural syntax:
f(x):=(2x)^(1/3); f''(1.99) For a large number of derivatives, for example 5, run diff(f(x),x,5)(x=1.99) 

05232015, 04:11 PM
Post: #8




RE: How to evaluate f'' at a specific point?
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!


05232015, 04:19 PM
Post: #9




RE: How to evaluate f'' at a specific point?
Can this syntax be used in the function graphing app...the diff(f(x),x,2) form? What is the proper syntax for this?


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