<Text-field style="Heading 1" layout="Heading 1"><Font encoding="UTF-8">Di\357\254\203eties</Font></Text-field>

coordinates([t,x], [u], 6);

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equation(u_t = u_xxx + 6*u*u_x);

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u_t;

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u_tx;

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u_tt;

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u_xxx;

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equation();

u_t;

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<Text-field style="Heading 2" layout="Heading 2">What can be on the left-hand side?</Text-field>

Every equation must be resolved with respect to a leading derivative q_X.

This means that neither q_X nor either of its derivatives q_XY occurs on the right-hand side:

equation('u_x' = (u_t - u_xxx)/6*u); # forbidden!

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u_xx;

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equation();

<Text-field style="Heading 2" layout="Heading 2">Equations dependent on functions </Text-field>

dependence(f(x,u));

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equation('u_t' = u_xxx + f*u_x);

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u_tx;

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f := x*u;

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u_tx;

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eval(u_tx);

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refresh();

u_tx;

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<Text-field style="Heading 2" layout="Heading 2">Multiple equations</Text-field>

coordinates([t,x], [u,v], 6);

equation(u_t = F, v_x=G);

u_t, v_x;

u_tx, v_tx;