[m] ∫ _{L}(2x+y)dl=∫ _{0}^{\frac{π}{2}}\sqrt{(6cos^2t\cdot (-sint))^2+(6sin^2t\cdot (cost))^2}dt=∫ _{0}^{\frac{π}{2}}\sqrt{6sin^2t \cdot cos^2t(cos^2t+sin^2t)}dt=[/m]
[m]=∫ _{0}^{\frac{π}{2}}\sqrt{6}sint cost dt=\sqrt{6} ∫ _{0}^{\frac{π}{2}}sint d(sint)=\sqrt{6}\cdot( \frac{sin^2t}{2})| _{0}^{\frac{π}{2}}=\frac{\sqrt{6}}{2}[/m]