Answer
1 rad/sec
Work Step by Step
We have:
$y=x^2$
$\tan\theta=\frac{y}{x}$
Using the Pythagorean Theorem:
$\tan\theta =\frac{x^2}{x}=x$ and given $dx=10\frac{m}{sec}$
on differentiating the above:
$\sec^2\theta d\theta=dx$
$d\theta=\frac{dx}{ \sec^2\theta}=\frac{10}{(\frac{\sqrt(90)}{3})^2}=1 rad/sec$
Thus, the final answer is: 1 rad/sec