Answer
$sin^{-1}(\theta-1)+C$
Work Step by Step
$\int \frac{d\theta}{\sqrt {2\theta-\theta^{2}}}=\int\frac{d\theta}{\sqrt {1-(\theta-1)^{2}}}$
Put $\theta-1=x$
Then $\frac{dx}{d\theta}= 1$ or $dx=d\theta$
Therefore, $\int \frac{d\theta}{\sqrt {2\theta-\theta^{2}}}=\int \frac{dx}{\sqrt {1-x^{2}}}=sin^{-1}(\frac{x}{1})+C$
$=sin^{-1}(\theta-1)+C$