Differentiation Equation- result of Derivative

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vu ngothanh
vu ngothanh 2015-4-16
评论： vu ngothanh 2015-4-16
I have i math like this:
L=5
x=5*L^2 %x=125
I need to have a result of y; y=diff(x)=50
What is the code that I must type to have result y=50; Thanks in advance

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Mischa Kim
Mischa Kim 2015-4-16
Vu, I believe what you are trying to do is this:
syms y(x) % define y as a function of x symbolically
L = 5;
y = 5*x^2; % define the function y
dy = diff(y,x); % compute its derivative
dyL = subs(dy,x,L) % compute the derivative at x = L
You'd need to have access to the Symbolic Math Toolbox to run the code.
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vu ngothanh
vu ngothanh 2015-4-16
Mr. Mischa Can you help again. I have a same requirement like the one upper. but now is multi variable like this. m,w,k,E,mI,c is constant
a=(((m*w^2-k)/(E*mI))^2+(c*w/(E*mI))^2)^(1/8);
b= atan(-c*w/(m*w^2-k))/4+pi/4;
X=a*cos(b);
Y=a*sin(b);
sa=cosh(L*X)*cos(L*Y);
sb=sinh(L*X)*sin(L*Y);
HOw can I get X',Y',sa',sa'.
Thank you very much

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