QuestionSolve for $\theta$ using the substitution $y=9 \cos \theta$ in the equation $\sqrt{81-y^{2}}$.

Studdy Solution
Since $\theta$ is in the range of $[0, \pi]$, $\sin \theta$ is always positive. So, we can drop the absolute value sign.
$$9 \sin \theta$$So, the simplified form of the given equation $\sqrt{81-y^{2}}$ using the substitution $y=9 \cos \theta$ is $9 \sin \theta$.