FindMaximum failing

Questions
,
1

Hi all..

I am trying to find the maximum point for the following graph.. it is visually clear that it is around 1300..

I was wondering whats the command for it…

Is it FindMaximum [{Cp[[Delta]]}, {[Delta], 0, 1}]]? i tried this and it dint work ..

Any help would help..

Thanks in advance..

Untitled.bmp (171 KB)

2

Find derivative

D[Cp[\[Delta]], \[Delta]]

Then solve

Solve[D[Cp[[Delta]], [Delta]]==0, [Delta]]

This will give value of delta at maximum.

3

Sorry…I get an error when i tried that command… Is it something like what i have attached in the file..?

4

actually no output displays..

5

(1) Post actual code with the question. A picture of code is not a usable substitute.

(2) From the notebook I can see there is an undefined \[Mu]m (as well as an unused \[Mu]p).

(3) The Solve syntax is incorrect. While this is not a forum for issues of basic Mathematica syntax,
I will remark that you get no output because the input never reaches the stage of evaluation.

(4) You define Cp as a function of a dummy variable delta. Also it has Npwhich uses a delta in its definition.
But these are not the same because it is not that dummy variable: you have a scoping problem. Here is what I mean.

Cp[t]

(* Out[21]= -((
 13.2 (-1 + t) (56250. \[Delta]^2 + 24496. \[Delta] \[Mu]m - 
    18723. \[Delta]^2 \[Mu]m - 480. \[Mu]m^2 + 
    540. \[Delta] \[Mu]m^2 - 
    135. \[Delta]^2 \[Mu]m^2))/(\[Delta] (168. \[Delta] - 
    9. \[Delta]^2 + 160. \[Mu]m - 180. \[Delta] \[Mu]m + 
    45. \[Delta]^2 \[Mu]m))) *)
6

Hello,
While at risk of encouraging those who do not read the posting guidelines or the documentation…

Pn = 40;
\[Mu]p = 0.2;
cp = -Pn (
  0.066 (56250.` \[Delta]^2 + 24496.` \[Delta] \[Mu]m - 
     18723.` \[Delta]^2 \[Mu]m - 480.` \[Mu]m^2 + 
     540.` \[Delta] \[Mu]m^2 - 
     135.` \[Delta]^2 \[Mu]m^2))/(\[Delta] (168.` \[Delta] - 
     9.` \[Delta]^2 + 160.` \[Mu]m - 180.` \[Delta] \[Mu]m + 
     45.` \[Delta]^2 \[Mu]m)) (\[Delta] - 1)/\[Mu]p
temp = cp /. \[Mu]m -> 1
Plot[temp, {\[Delta], 0, 1}]
FindMaximum[temp, \[Delta]]

with hopes that I can get someone to look at my CUDA questions on community… sigh.
WCC

7

Sorry in the first hand. yes! i missed to paste the [Mu]m , i was only not sure with the command to be used.
may be i should read the posting guidelines.. i am only learning mathematica. is there a rule that i cannot ask basic or east questions in this forum?

8

I pasted the picture, only to show what i really want to ask. in this case the syntax to be used..

  1. is there even a rule that i cannot ask basic or easy questions in this forum?? in that case, it is a pity for beginners .
9

but thanks it helped. i was only asking if FindMaximum would work.. it worked when i wrote it after plot syntax.

10

Hello Ash Ash,

I am sorry if my response appeared to be rude to you. It was not my intention. Danny is correct that the probability of getting a response is increased if code can be cut-and-pasted from the post.

I believe that basic questions should be encouraged. However, if the poster makes an effort (to fix syntax, look for a working example in the documentation, and make sure that all variables which be defined are defined), that effort will be rewarded by learning.

11

Thanks..

I just have a follow up question..

What would be the command in case if delta is known..
for example, delta = 0.3 and I need to get the corresponding y axis value..

12

Hello Ash Ash,
Perhaps I misunderstand your question. I am assuming that you are no longer interested in a maxima.

To find the value of an expression for a particular value of a parameter, you can use slash-dot with a rule:

 expr = a Cos[ b x]
   
 expr /. a -> 2
   
 expr /. {a -> 2, x -> 3}
   
 expr /. {a -> 2, b -> 3, x -> Pi}

More information can be found here: tutorial/ApplyingTransformationRules

13

thanks! that was clarifying! :slight_smile: