1 years, 86 days

## Using coeff and subs function...

Maple

I have the following code below:

eq := -((2*(alpha[3]+alpha[2]))*((1/2)*cos(Theta(z, t))^2-(1/2)*sin(Theta(z, t))^2)+(alpha[3]-alpha[2])*(sin(Theta(z, t))^2+cos(Theta(z, t))^2))*(diff(U(z, t), z))-(alpha[3]-alpha[2])*(2*sin(Theta(z, t))^2*(diff(Theta(z, t), t))+2*cos(Theta(z, t))^2*(diff(Theta(z, t), t)))+(diff(Theta(z, t), z, z))*k

simplify(subs(simplify(coeff(eq, diff(U(z, t), z))) = t1, eq))

Please, why is maple not assigning t1 to the coefficient of diff(U(z, t), z)) in the expression?

## How to use "collect"...

Maple

Hi, I have the equation below and I'm trying to use "collect " to get the coefficient of dudy^2 and dvdx^2. I tried

aa1 := subs({gamma[1] = alpha[3]-alpha[2], gamma[2] = alpha[6]-alpha[5]}, collect(aa, {dudy^2, dvdx^2}))

But is not collecting the coefficient of dvdx^2. Please can someone help?

## summing number using sequence...

Maple

Please, how do I fix this? I have

n := Vector[row]([cos(theta(x, y, t)), sin(theta(x, y, t))]);

and Tried :

sum(Multiply(n[i], n[i]), i = 1 .. 2)

## How to compute divergence and curl of 2D...

Maple

Please how do I compute the div n,  (n.curl n), (n.curl n)^2 and (n x curl n) and  (n x curl n)^2 given the information below:

restart; restart; with(VectorCalculus); with(LinearAlgebra);

I.e.,

n = (cos(theta(x,y), sin(theta(x,y), 0).

I tried

divn := Divergence(proc (x, y, z) options operator, arrow; `<,>`(n) end proc);

but received: Error, (in VectorCalculus:-Divergence) the procedure must evaluate to a Vector

Maple