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+--- Thread: another fsolve question (/thread-4194.html)
another fsolve question - roadrunner - 06-20-2015 04:01 PM
Can anyone tell me what I am doing wrong?
I plotted the function ph2o(X) (code below) and touched Menu/Fcn/Tangent and, as expected, I saw the tangent line at the cursor location that I could trace up and down the curve.
[attachment=2185]
However, when I plot function tdew(X,15) (code also below) and touch the tangent soft-key I get nothing. When I touch slope I get NaN.
[attachment=2187]
I get the same result with newton, newtonj, and bisection solver. Am I doing something wrong, or is the calculator not capable of that operation on that function?
Thanks for reading,
Paul
Code:
EXPORT ph2o(temp)
BEGIN
local a,b;
b:=(temp+273.15)/273.16;
a:=1-1/b;
return 10^(10.79574*a-5.028*log(b,10)+
1.50475ᴇ−4*(1-10^(−8.2969*(b-1)))+
4.2873ᴇ−4*(10^(4.76955*a)-1)-0.2138602);
END;
export tdew(r,tamb)
begin
LOCAL y,z;
r:=ph2o(tamb)*r/100;
z:="fsolve(ph2o(x)="+STRING(r,2,12)+",x,−50 .. 100, newton_solver)";
y:=CAS(z);
RETURN y(1);
END;