\[\tan\left(az\right)=\cfrac{a\tan z}{1+\cfrac{(1-a^{2}){\tan}^{2}z}{3+\cfrac{(4%
-a^{2}){\tan}^{2}z}{5+\cfrac{(9-a^{2}){\tan}^{2}z}{7+}}}}\cdots,\]