MATLAB Symbolic math toolbox

Question

Blake Sewell 2020-10-14

0
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https://ww2.mathworks.cn/matlabcentral/answers/613626-matlab-symbolic-math-toolbox

评论： Ameer Hamza 2020-10-14

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Hi, I am having troubles with using the symbolic math toolbox to figure out the following:

I have code which doesnt use the symbolic math toolbox which gets the correct graph and also code which attempts to use the symbolic math toolbox but does not work:

Working code without symbolic toolbox:

t = 1:1:10;
s = ((6/5).*(t.^3)-(81/5).*(t.^2)+(252/5).*(t));
velocity = diff(t); %first derivative is velocity
%d/dx of s = 3.6t^2-32.4t+50.4
plot (s)
xlabel('Time (seconds)');
ylabel('Displacement (metres)');
%turning point @ (5,-22.2) on graph
%roots=turning point 
p = [3.6 -32.4 50.4];
r = roots(p);
disp (r)

Non-working code using symbolic math toolbox:

syms t
s = sym(6/5).*(t.^3)-(81/5).*(t.^2)+(252/5).*(t);
v = diff(s); %first derivative is velocity
%d/dx of s = 3.6t^2-32.4t+50.4
fplot (t,v)
xlim([0 10])
ylim([-50 100])
xlabel('Time (seconds)');
ylabel('Displacement (metres)');
%turning point @ (5,-22.2) on graph
%roots=turning point 
p = [3.6 -32.4 50.4];
r = roots(p);
disp (r)