Chapter 6 Partial Differential Equations
Chapter 6 Partial Differential Equations
Chapter 6 Partial Differential Equations
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
52 CHAPTER 6. PARTIAL DIFFERENTIAL EQUATIONS<br />
Exercise Set 2: Classification and Canonical Forms<br />
1. Classify the operators and find the characteristics (if any) through the point (0, 1):<br />
(a) u tt + u xt + u xx =0<br />
(b) u tt +4u xt +4u xx =0<br />
(c) u tt − 4u xt + u xx =0<br />
2. Find where the operators are hyperbolic, parabolic and elliptic:<br />
(a) Lu = u tt + tu xx + xu x<br />
(b) Lu = x 2 u tt − u xx + u<br />
(c) Lu = tu tt +2u xt + xu xx + u x<br />
3. Transform the equation to canonical form: 2u xx − 4u xy − 6u yy + u x =0.<br />
4. Transform the equations to canonical form:<br />
(a) e 2x u xx +2e x+y u xy + e 2y u yy + u x =0.<br />
(b) x 2 u xx + y 2 u yy = 0 for x>0, y>0.<br />
5. Transform the equations to canonical form:<br />
(a) u xx +2u xy +17u yy =0.<br />
(b) 4u xx +12u xy +9u yy − 2u x + u =0.<br />
6. Find the characteristics of Lu = u tt − tu xx through the point (0, 1).<br />
7. Determine where the following equation is hyperbolic or parabolic.<br />
yu xx +(x + y)u xy + xu yy =0<br />
Where the equation is hyperbolic, show that the general solution may be written as<br />
u(x, y) = 1 ∫<br />
f(β) dβ + g(y − x).<br />
y − x<br />
where β = y 2 − x 2<br />
8. Classify the following equation and find the canonical form, u xx − 2u xt + u tt =0. Show<br />
that the general solution is given by u(x, t) =tf(x + t)+g(x + t).<br />
9. Show that (1 + x 2 )u xx +(1+y 2 )u yy + xu x + yu y = 0 is elliptic and find the canonical<br />
form of the equation.