Решите :
1. (tg α/ctg α) + 1 =
2. (sin^2 α - 1) / (1 - cos^2 α) =

1. (tg α/ctg α) + 1 =tgα·tgα+1=tg²α+1=1/cos²α2. (sin² α - 1) / (1 - cos² α) =(1-cos²α-1)·sin²α=-cos²α·sin²α=-4 cos²α·sin²α/4==-sin²2α/4