## Calculus (3rd Edition)

$2 \sin \sqrt t +C$
Substitute $u=\sqrt t$. This implies $t=u^{2}$. $⇒\frac{dt}{du}=2u$ or $dt= 2udu$ Then, $\int \frac{\cos \sqrt t}{\sqrt t}dt=\int \frac{\cos u}{u}2udu$ $=2\int \cos u du= 2\sin u+C$ $=2\sin \sqrt t+C$