∫ dx/(1+x²)²
令x=tant,dx=sec²t dt
原式=∫ sec²t/(1+tan²t)² dt
=∫ sec²t/(sec²)² dt
=∫ cos²t dt
=(1/2)∫ (1+cos2t) dt
=(1/2)(t+1/2*sin2t) + C
=(1/2)t + (1/2)sintcost + C
=(1/2)arctanx + (1/2)[x/√(1+x²)][1/√(1+x²)] + C
=(1/2)[x/(1+x²)+arctanx] + C
∫ dx/(1+x²)²
令x=tant,dx=sec²t dt
原式=∫ sec²t/(1+tan²t)² dt
=∫ sec²t/(sec²)² dt
=∫ cos²t dt
=(1/2)∫ (1+cos2t) dt
=(1/2)(t+1/2*sin2t) + C
=(1/2)t + (1/2)sintcost + C
=(1/2)arctanx + (1/2)[x/√(1+x²)][1/√(1+x²)] + C
=(1/2)[x/(1+x²)+arctanx] + C