\[\boxed{\mathbf{1250}\mathbf{.}}\]
\[1)\sin\left( \pi - \arcsin\frac{3}{4} \right) =\]
\[= \sin\left( \arcsin\frac{3}{4} \right) = \frac{3}{4}\]
\[2)\sin\left( \pi + \arcsin\frac{2}{3} \right) =\]
\[= - \sin\left( \arcsin\frac{2}{3} \right) = - \frac{2}{3}\]