$\begin{array}{rcll} -10 \sin\left( x \right) -5&=&0&\quad|\ +5\\ -10 \sin\left( x \right) &=&5&\quad|\ :\left(-10\right)\\ \sin\left( x \right) &=&-\frac{1}{2}&\quad|\ \sin^{-1}\\ x&=&\sin^{-1}\left(-\frac{1}{2}\right)&\end{array}$
1. Nullstelle:
$x=-0{,}52$