I am trying to solve for OS here, but keeping getting pi/2 even when I change L

%variables

F = .00024; %kg

E = 10^6; %mPa

I = 6.1*10^-9; %kg m^2

L = .01; %m

%solve for Theta sub 0

func = @(initial) L/sqrt((E*I)/(2*F)) - integral(@(theta)1./sqrt(cos(initial)-cos(theta)),initial,pi/2);

OS = fsolve(func,.5);

I am not sure what I am doing wrong here, I hope to find the value of initial, this function is in respect to d theta. Is there anything wrong with this?

I want to then solve for xi which is also funky,

aa = linspace(pi/2*.99, 0, 49);

aa=aa';

%shape of rod given

xi = sqrt((2*E*I)/F)*(sqrt(cos(OS))-sqrt(cos(OS)-cos(aa)));

any help appreciated not sure what is wrong

Answer 1

[Jeffrey Clark]

@adam puchalski, you need to limit fsolve such that it doesn't attempt values that cause sqrt(cos(initial)-cos(theta)) to return a complex value, e.g., values >pi/2 and other ranges about the circle:

func(2)

ans =

0.0028 - 1.3565i