Problem using the Secant Method

Question

Yianni 2014-11-7

0
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https://ww2.mathworks.cn/matlabcentral/answers/161656-problem-using-the-secant-method

评论： Star Strider 2014-11-7

I want to solve a problem in which I am given a function (seen below) where W is 250 and I must find x. I have to use the secant method but I am having trouble with this as I only know how to find the roots. How can I do this?

% Function that determines the weight or downward force(W) of an object
% with a chosen vertical deflection value "x" in m.
function W = weight(x)
a = 0.15;                   %Constant value "a"
b = 0.05;                   %Constant value "b"
K = 2800;                   %Force of springs in N/m
L = sqrt(a^2+(b+x)^2);      %Hypotenuse Length of Right Triangle
Lo = sqrt(a^2+b^2);         %Unstretched Length
dL = L-Lo;                  %Difference of Stretched vs Unstretched Length
SINtheta = (b+x)/L;         %Length of side opposite angle theta/Hypotenuse
W = 2*K*dL*SINtheta;        %Downward force due to weight in N
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