Newton's method(calculating theta)

Question

Ahmed Alhawaj 2020-3-16

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/511039-newton-s-method-calculating-theta

回答： Sriram Tadavarty 2020-3-16

采纳的回答： Sriram Tadavarty

w = 30; h = 30; b = 3.5; % In inches

f = @(theta) w*sind(theta) - h*cosd(theta) - b;

fp = @(theta) w*cosd(theta)+h*sind(theta);

theta_newt(1) = 49.76; % Set initial guess

tol=0.4771;

n=1;

while n<=1:50

fe = f(theta_newt(1));

fpe = fp(theta_newt(1));

theta_newt(n+1) = theta_newt(n) - fe(n)/fpe(n);

if theta_newt(n+1)< 49.73-tol || theta_newt(n+1)>49.73+tol

return

else

theta=theta_newt(n+1);

end

n=n+1;

end

disp(theta)

why is the code not returning to the loop when it is not calculating the wanted angle?

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Answer 1

Sriram Tadavarty 2020-3-16

0
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/511039-newton-s-method-calculating-theta#answer_420272

Hi Ahmed,

The condition you placed for the while loop is a series of vector. Update the condition as below and code requires minor modifications to work

while n <= 50 % It runs the loop till n becomes 50
    fe = f(theta_newt(n));
    fpe = fp(theta_newt(n));
    theta_newt(n+1) = theta_newt(n) - fe/fpe;
    if theta_newt(n+1)< 49.73-tol || theta_newt(n+1)>49.73+tol
        return
    else
        theta=theta_newt(n+1);
    end
    n=n+1;
end