Pretty simple on fzero

I keep getting an error with the code bellow. I've gonna about this a couple of different way but still nothing. What I'm i going wrong?

function Trim

%Givens
delta=60000; %lbs
LCG=29; %ft
b=14; %ft
B=18; %degrees
V=67.5; %ft/s
a=1.39; %dt
f=0.5; %ft
e=4; % degrees
v=1.052e-5; 

global x

%---------EQ's-------------

%C--------
Cv=3.18;
lamda= 64.267./ x^2.2;

C= LCG-(0.75-1./(5.21*(Cv./lamda)^2+2.39)*lamda*b);

%Df-------

V1= V*(1-0.0675./(lamda*cosd(x)))^(1/2);
Lk= lamda*b+(b*tand(B))./(2*pi*tand(x));
Re= V1*Lk./v;
Cf=0.075./(log10(Re)-2)^2;
Df= Cf*1.99*V1^2*lamda*b^2./(2*cosd(B));

%solve for Trim-------

X=fzero(@(x) delta.*((1-sind(lamda).*sind(x+e))./cosd(x).*C-f.*sind(x))+Df.*(a-f), 4)

end

[Geoff Hayes]

Adam - please post the full error message that you are observing and, in particular, the line number that is generating the error.

[Adam Stofko]

Operands to the and && operators must be convertible to logical scalar values.

Error in fzero (line 308) elseif ~isfinite(fx) ~isreal(fx)

Error in Trim (line 37) X=fzero(@(x) delta.*((1-sind(lamda).*sind(x+e))./cosd(x).*C-f.*sind(x))+Df.*(a-f), 4)

[Geoff Hayes]

Adam - in the line

 global x

what is x defined to be? If it hasn't been defined, then it is an empty matrix and so lambda is initialized to an empty matrix too. This seems to cause the error that you are observing. Please verify that x is initialized correctly and review whether it should be a global variable or just a local variable or an input to this function.

Answer 1

[Torsten]

    function call

    X0=4;
    X=fzero(@f,X0);

    function y=f(x)

    delta=60000; %lbs
    LCG=29; %ft
    b=14; %ft
    B=18; %degrees
    V=67.5; %ft/s
    a=1.39; %dt
    f=0.5; %ft
    e=4; % degrees
    v=1.052e-5; 

    %---------EQ's-------------

    %C--------
    Cv=3.18;
    lamda= 64.267./ x^2.2;

    C= LCG-(0.75-1./(5.21*(Cv./lamda)^2+2.39)*lamda*b);

    %Df-------

    V1= V*(1-0.0675./(lamda*cosd(x)))^(1/2);
    Lk= lamda*b+(b*tand(B))./(2*pi*tand(x));
    Re= V1*Lk./v;
    Cf=0.075./(log10(Re)-2)^2;
    Df= Cf*1.99*V1^2*lamda*b^2./(2*cosd(B));

    y=delta.*((1-sind(lamda).*sind(x+e))./cosd(x).*C-f.*sind(x))+Df.*(a-f);

    end

Best wishes

Torsten.