令x=asinu,√(a²-x²)=acosu,则dx=acosudu原式=∫ a²cos²udu=a²/2∫ (1+cos2u)du=a²/2(u+1/2sin2u)+C=a²u/2+(a²/2)sinucosu+C由x=asinu,√(a²-x²)=acosu,得：sinu...