Testing of computations

• Use two independent methods!  (This is done in practice!)
• If one method only works for special cases, use it for those!

• visual
• most problems can be visualized in 2 dimensions
• behaviour of functions of 1 variable (keep all others constant)
• also, intersection between curves, common tangents, zeros of functions
• 4.9 in Horstmann shows intersection between line and circle
• analytical
• take a paper and pencil!
• ... or Mathematica or Maple:  learning either or both can save a lot of time using a pocket calculator
• at the very least for a special case
• cf. 4.9 in Horstmann
• numerical
• E.g., if you calculated an integral by hand, check it by a numerical integration
• Example in 4.9:  step along line and calculate distance to the center of the circle;  check at what point distance is equal to radius