In exercises $21-26$ solve the given Fredholm integral equations by using the noise terms phenomenon :

$u(x)=\frac{sinx}{1+sinx}+x-\frac{}{2}x+{\displaystyle \underset{0}{\overset{\frac{}{2}}{}}}xu(t)dt.$

$u(x)=\frac{sinx}{1+cosx}-xln(2)+{\displaystyle \underset{0}{\overset{\frac{}{2}}{}}}xu(t)dt.$

$u(x)=\frac{se{c}^{2}x}{1+tanx}-xln(2)+{\displaystyle \underset{0}{\overset{\frac{}{4}}{}}}xu(t)dt.$