Problem 397

41. In $\triangle A B C$, it is known that $\angle A=60^{\circ}$, the $n$-section lines of $\angle A B C$ and the $n$-section lines of $\angle A C B$ intersect at $G_{1}$, $G_{2}$, $G_{3}$, $\cdots$, $G_{n-1}$. When $n=10$, $\angle B G_{9} C=$ $\qquad$ degrees. (where the integer $n \geqslant 2$)