Question

Выражение1+ctg(2альфа-3/2пи)ctg(3/2пи+альфа)

Answer 1

1+ctg(2alfa-1.5pi)*ctg(1.5pi+alfa)

ctg(2alfa-1.5pi+1.5pi+alfa)+1

ctg(3alfa)+1

Answer 2

$1+ctg(2\alpha-\frac{3}{2}\pi)\cdot ctg(\frac{3}{2}\pi+\alpha)=1-ctg(\frac{3}{2}\pi-2\alpha)\cdot ctg(\frac{3}{2}\pi+\alpha)=$

$=1-tg2\alpha\cdot(-tg\alpha)=1+tg2\alpha\cdot tg\alpha=1+\frac{sin2\alpha}{cos2\alpha}\cdot \frac{sin\alpha}{cos\alpha}=$

$=1+\frac{2\cdot sin\alpha\cdot cos\alpha\cdot sin\alpha}{cos2\alpha\cdot cos\alpha}=1+\frac{2\cdot sin^2\alpha}{cos2\alpha}=1+\frac{1-cos2\alpha}{cos2\alpha}=\frac{cos2\alpha+1-cos2\alpha}{cos2\alpha}=$

$=\frac{1}{cos2\alpha}$