Question

1-ctg альфа/tg альфа-1

Answer 1

1-ctg$\alpha$/tg$\alpha$-1 = (sin$\alpha$ - cos$\alpha$) * cos$\alpha$ / (sin$\alpha$ - cos$\alpha$) * sin$\alpha$ = cos$\alpha$/sin$\alpha$ = ctg$\alpha$
ctg$\alpha$ = cos$\alpha$/sin$\alpha$
tg$\alpha$ = sin$\alpha$/cos$\alpha$
1-ctg$\alpha$ = sin$\alpha$ - cos$\alpha$/sin$\alpha$
tg$\alpha$-1 = sin$\alpha$ - cos$\alpha$/cos$\alpha$