∫ ( c o s x ) d x {\displaystyle \int (cos{\sqrt {x}})dx} = 2 x ∫ ( c o s u ) d u {\displaystyle 2{\sqrt {x}}\int (cosu)du}
{u} = x {\displaystyle {\sqrt {x}}}
{du} = 1 2 x d u {\displaystyle {\frac {1}{2{\sqrt {x}}}}du}
