求积分sqrt(1+x^2)

令x=tan(t)dx=1/cos^2(t)dt积分sqrt(1+x^2)dx=积分1/cos^3(t)dt=积分1/cos^4(t)d(sin(t))=积分1/(1-sin^2(t))^2d(sin(t))=1/4(ln(sin(t)+1)-1/(sin(t)+1)-ln(sin(t)-1)-1/(sin(t)-1))+C再将sin(t)=1/(1+1/x^2)^0.5代...