[m] ∫_{0}^{\frac{π}{4}}\sqrt{ 1+\frac{sin^2x}{cos^2x}}dx=∫_{0}^{\frac{π}{4}}\sqrt{ \frac{cos^x+sin^2x}{cos^2x}}dx=∫_{0}^{\frac{π}{4}}\sqrt{ \frac{1}{cos^2x}}dx=∫_{0}^{\frac{π}{4}}\frac{1}{cosx}dx=[/m]
табличный
[m]=(ln|tg(\frac{x}{2}+\frac{π}{4})|)|_{0}^{\frac{π}{4}}=ln tg\frac{3π}{8}-lntg\frac{π}{4}=ln tg\frac{3π}{8}-ln1=ln tg\frac{3π}{8}[/m]