d1=0.45;
λ1=0.8;
λiz=0.04;
α1=5;
α2=23;
Rt1=(1/(α2*S));
Rt3=(1/(α1*S));
Rt2=(d1/(λ1*S));

vykon1=((ΔT)/(Rt1+Rt2+Rt3));
Rtiz=(diz/(λiz*S));
vykon2=((ΔT)/(Rt1+Rt2+Rt3+Rtiz));
dosIz=Solve[(vykon1/vykon2)==3][[1]]

Tin=25;
Texter=-12;
Q=((Tin-Texter)/(Rt1+Rt2+Rt3+Rtiz))/.dosIz;

T1=Tin-Q*Rt3//Simplify;
T2=(Tin-Q*(Rt3+Rt2)//Simplify)/.dosIz;
T3=(Tin-Q*(Rt3+Rt2+Rtiz)//Simplify)/.dosIz;
T4=(Tin-Q*(Rt3+Rt2+Rtiz+Rt1)//Simplify)/.dosIz;
{T1,T2,T3,T4}

vyr[x_]:=a*x+b;
resab=Solve[{vyr[-1]==λiz,vyr[1]==λ1}][[1]]

dmax=0.0645+0.45;
lambda[x_]=a*Tanh[((x-0.0645)/0.001)]+b/.resab;
Plot[lambda[x],{x,0,0.7},AxesOrigin->{0,0}];
rce=0==D[lambda[x]*D[T[x],x],x];
res[der0_]:=T[x]/.NDSolve[{rce,T[0]==-11.3,T'[0]==der0},T[x],{x,0,dmax},MaxStepSize->0.001dmax][[1]]
res[1]

tepl=res[300];
Plot[tepl,{x,0,dmax},PlotRange->All]

Plot[{Log[x],((x^2)-1)*0.1},{x,1,10}]

Rtheta=(1/(2*λ*delka*Pi))*Log[(r2/r1)]+(1/(α*2*Pi*r2*delka));
D[Rtheta,r2]//Simplify
Solve[Numerator[%]==0,r2]

(λ/α)/.{λ->.04,α->23}