Question

Упростить выражение:
cos x * tg(180° + x)*tg(270° - x)

Answer 1

$\displaystyle\bf\\Cosx\cdot tg\Big(180^\circ+x\Big)\cdot tg\Big(270^\circ-x\Big)=Cosx\cdot \underbrace{tgx\cdot Ctgx}_{1}=\\\\=Cosx\cdot 1=Cosx$