nothing appears with this code

Question

Hyunji Yu 2020-3-8

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/509720-nothing-appears-with-this-code

回答： Star Strider 2020-3-8

syms t;
x(t) = sin(3*t^2)*(12*t + (10*13^(1/2))/13);
y(t) = t*(6*13^(1/2)*t + 5);
z(t) = cos(3*t^2)*(12*t + (10*13^(1/2))/13);
%Length of the curve - Arc Length
speed(t) = sqrt(diff(x(t),t)^2 + diff(y(t),t)^2 + diff(z(t),t)^2);
speedsim(t) = prod(sqrt(factor(simplify(expand(speed(t)^2)))));
int(speed(t),t, 0, 2*pi);

I'm trying to find Arc Length in numerical value, but it doesn't work. Nothing appears when I click start button. Also, I don't know what to add to get numerical value because it seems like it would appear just a formula.

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Answer 1

Star Strider 2020-3-8

0
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/509720-nothing-appears-with-this-code#answer_419105

在 MATLAB Online 中打开

Use vpaintegral instead of int:

syms t;
x(t) = sin(3*t^2)*(12*t + (10*13^(1/2))/13);
y(t) = t*(6*13^(1/2)*t + 5);
z(t) = cos(3*t^2)*(12*t + (10*13^(1/2))/13);
%Length of the curve - Arc Length
speed(t) = sqrt(diff(x(t),t)^2 + diff(y(t),t)^2 + diff(z(t),t)^2);
speedsim(t) = prod(sqrt(factor(simplify(expand(speed(t)^2)))));
AL = vpaintegral(speed,t, 0, 2*pi)