Hi everyone,
I have a question for help. I define
phi1=function('phi1',x,y,t)
phi2=function('phi2',x,y,t)
phi3=function('phi3',x,y,t)
psi=function('psi',x,y,t)
x0=function('x0',x,y,t)
y0=function('y0',x,y,t)
theta=function('theta',x,y,t)
phi1=cos(theta)*(x-x0)+sin(theta)*(y-y0)
phi2=((-cos(theta)+sqrt(3)*sin(theta))*(x-x0)+(-sqrt(3)*cos(theta)-sin(theta))*(y-y0))/2
phi3=((-cos(theta)-sqrt(3)*sin(theta))*(x-x0)+(sqrt(3)*cos(theta)-sin(theta))*(y-y0))/2
then I define a set equations of:
eq1=diff(phi1,t)==diff(psi,x)*diff(phi1,x)+diff(psi,y)+diff(phi1,y).......
which are too long, I don't list them here.
then I use
eq1.subsitute.expression(diff(theta,t)==tt,diff(x0,t)==xt,diff(y0,t)==yt)
solve([eq1,eq2,eq3],tt,xt,yt)
to get the equations of tt, xt and yt.
the results are
[tt=r1, xt=(D[0](theta)(t, x, y)^2....)]
my question is, here the D[0](theta)(t,x,y)^2 is the derivative to
t or to x? I guess it is still the derivative to x, because
diff(theta(t,x,y),x) still got D[0](theta)(x,y,t),
but I am not sure. So can anyone help me with that?
thanks in advance!
YC
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