Chapter         7 Integration Techniques, L’Hospital Rule, and Improper Integrals
7.3 Partial Fractions
7.1 Basic Integration Formulas
7.2 Integration by Parts
  7.4 Trigonometric Substitutions
7.5 Integral Tables, CAS, and Monte Carlo    Integration
7.6 L’ Hospital Rule
7.7 Improper Integrals
7.6
L’ Hospital Rule(洛必达法则)
Consider the limit
where