2.4 Homogeneous Wave PDE in 2D. No source

  2.4.1 Rectangular membrane. Fixed on all edges
  2.4.2 circular membrane, no circular symmetry, example 1
   2.4.2.1 Animations
  2.4.3 circular membrane, no circular symmetry, specific problem from exam
  2.4.4 circular membrane, with circular symmetry