70 HFOPDE, chapter 3 examples

70.1 Example 1
70.2 Example 2
70.3 Example 3

____________________________________________________________________________________

70.1 Example 1

problem number 651

Added Feb. 9, 2019.

Problem Chapter 3, example 1 from Handbook of first order partial differential equations by Polyanin, Zaitsev, Moussiaux.

Solve for \(w(x,y)\)

\[ a x w_x + b y w_y = c \]

Mathematica

ClearAll[w, x, y, n, a, b, m, c, k, alpha, beta, gamma, A, C0, s, lambda, B, s, mu, d, g, B, v, f, h]; 
 pde = a*x*D[w[x, y], x] + b*y*D[w[x, y], y] == c; 
 sol = AbsoluteTiming[TimeConstrained[DSolve[pde, w[x, y], {x, y}], 60*10]];
 

\[ \left \{\left \{w(x,y)\to \frac {a c_1\left (y x^{-\frac {b}{a}}\right )+c \log (x)}{a}\right \}\right \} \]

Maple

 
w:='w';x:='x';y:='y';a:='a';b:='b';n:='n';m:='m';c:='c';k:='k';alpha:='alpha';beta:='beta';g:='g';A:='A';f:='f'; 
C:='C';lambda:='lambda';B:='B';mu:='mu';d:='d';s:='s';v:='v'; 
pde := a*x*diff(w(x,y),x)+ b*y*diff(w(x,y),y) = c; 
cpu_time := timelimit(60*10,CodeTools[Usage](assign('sol',pdsolve(pde,w(x,y)) ),output='realtime'));
 

\[ w \left ( x,y \right ) ={\frac {1}{a} \left ( c\ln \left ( x \right ) +{\it \_F1} \left ( y{x}^{-{\frac {b}{a}}} \right ) a \right ) } \]

____________________________________________________________________________________

70.2 Example 2

problem number 652

Added Feb. 9, 2019.

Problem Chapter 3, example 2 from Handbook of first order partial differential equations by Polyanin, Zaitsev, Moussiaux.

Solve for \(w(x,y)\)

\[ a e^x w_x + b w_y = c e^{2 x} y \]

Mathematica

ClearAll[w, x, y, n, a, b, m, c, k, alpha, beta, gamma, A, C0, s, lambda, B, s, mu, d, g, B, v, f, h]; 
 pde = a*Exp[x]*D[w[x, y], x] + b*D[w[x, y], y] == c*Exp[2*x]*y; 
 sol = AbsoluteTiming[TimeConstrained[DSolve[pde, w[x, y], {x, y}], 60*10]];
 

\[ \left \{\left \{w(x,y)\to \frac {a^2 c_1\left (\frac {e^{-x} \left (a e^x y+b\right )}{a}\right )+a c e^x y-b c x+b c}{a^2}\right \}\right \} \]

Maple

 
w:='w';x:='x';y:='y';a:='a';b:='b';n:='n';m:='m';c:='c';k:='k';alpha:='alpha';beta:='beta';g:='g';A:='A';f:='f'; 
C:='C';lambda:='lambda';B:='B';mu:='mu';d:='d';s:='s';v:='v'; 
pde := a*exp(x)*diff(w(x,y),x)+ b*y*diff(w(x,y),y) = c*exp(2*x)*y; 
cpu_time := timelimit(60*10,CodeTools[Usage](assign('sol',pdsolve(pde,w(x,y)) ),output='realtime'));
 

\[ w \left ( x,y \right ) ={\frac {y}{{a}^{2}} \left ( {{\rm e}^{x-{\frac {b{{\rm e}^{-x}}}{a}}}}{{\rm e}^{{\frac {b{{\rm e}^{-x}}}{a}}}}ac-\Ei \left ( 1,{\frac {b{{\rm e}^{-x}}}{a}} \right ) {{\rm e}^{{\frac {b{{\rm e}^{-x}}}{a}}}}bc \right ) }+{\it \_F1} \left ( y{{\rm e}^{{\frac {b{{\rm e}^{-x}}}{a}}}} \right ) \]

____________________________________________________________________________________

70.3 Example 3

problem number 653

Added Feb. 9, 2019.

Problem Chapter 3, example 3 from Handbook of first order partial differential equations by Polyanin, Zaitsev, Moussiaux.

Solve for \(w(x,y)\)

\[ w_x + a w_y = b \]

Mathematica

ClearAll[w, x, y, n, a, b, m, c, k, alpha, beta, gamma, A, C0, s, lambda, B, s, mu, d, g, B, v, f, h]; 
 pde = D[w[x, y], x] + a*D[w[x, y], y] == b; 
 sol = AbsoluteTiming[TimeConstrained[DSolve[pde, w[x, y], {x, y}], 60*10]];
 

\[ \left \{\left \{w(x,y)\to c_1(y-a x)+b x\right \}\right \} \]

Maple

 
w:='w';x:='x';y:='y';a:='a';b:='b';n:='n';m:='m';c:='c';k:='k';alpha:='alpha';beta:='beta';g:='g';A:='A';f:='f'; 
C:='C';lambda:='lambda';B:='B';mu:='mu';d:='d';s:='s';v:='v'; 
pde :=  diff(w(x,y),x)+a*diff(w(x,y),y) = b; 
cpu_time := timelimit(60*10,CodeTools[Usage](assign('sol',pdsolve(pde,w(x,y)) ),output='realtime'));
 

\[ w \left ( x,y \right ) =bx+{\it \_F1} \left ( -ax+y \right ) \]