Sin ^2 α / 1+ ctg ^2 α * (cos ^2 α -1)

Question

Sin ^2 α / 1+ ctg ^2 α * (cos ^2 α -1)

Answer 1

(sin²α/(1+ctg²α))*(cos²α-1)=(sin²α/(1/sin²α))*(-sin²α)=-sin⁶α.