# FindMaximum failing

Posted 9 years ago
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 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..
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Posted 9 years ago
 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?
Posted 9 years ago
 but thanks it helped. i was only asking if FindMaximum would work.. it worked when i wrote it after plot syntax.
Posted 9 years ago
 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.
Posted 9 years ago
 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..
Posted 9 years ago
 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
Posted 9 years ago
 thanks! that was clarifying! :)
Posted 9 years ago
 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
Posted 9 years ago
 (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))) *) 
Posted 9 years ago
 I pasted the picture, only to show what i really want to ask. in this case the syntax to be used..3) 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 .
Posted 9 years ago
 Find derivative D[Cp[\[Delta]], \[Delta]] `Then solve Solve[D[Cp[[Delta]], [Delta]]==0, [Delta]]This will give value of delta at maximum.
Posted 9 years ago
 Sorry...I get an error when i tried that command... Is it something like what i have attached in the file..? Attachments:
Posted 9 years ago
 actually no output displays..