tan(x=(a/b)/(1/3)
tan^2(x)=(a/b)^(2/3)
联立sin^2(x)/cos^2(x)=(a/b)^(2/3)
sin^2(x)+cos^2(x)=1
解得sin^2(x)=a^(2/3)/(a^(2/3)+b^(2/3))
cos^2(x)=b^(2/3)/(a^(2/3)+b^(2/3))
代入L得L=a*(a^(2/3)+b^(2/3))/a^(2/3)+b*(a^(2/3)+b^(2/3))/b^(2/3)
L=(a^(2/3)+b^(2/3))(a/a^(2/3)+b/b^(2/3))
=(a^(2/3)+b^(2/3))(a^(1/3)+b^(1/3))
=(a^(2/3)+b^(2/3))(a^(2/3)+b^(2/3))^(1/2)
=(a^(2/3)+b^(2/3))^(1+1/2)
=(a^(2/3)+b^(2/3))^(3/2)