(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 Np
which 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))) *)