Question

Срочно помогите упр 710(1,3) !!!!!!

Answer 1

$1);frac{cos(-alpha)+3cos180^o+cos(180^o-alpha)}{tan(-60^o)-cos(-120^o)-tan(-420^o)}=frac{cosalpha+3cdot(-1)-cosalpha}{-tan60^o-cos120^o+tan420^o}=\=frac{-3}{-tan60^o+frac12+tan(360^o+60^o)}=frac{-3}{-tan60^o+frac12+tan60^o}=frac{-3}{frac12}=-6$

$3);cos(-alpha)tan(alpha-180^o)-tan(-alpha):cos(180^o-alpha)=\=cosalphacdot(-tan(180^o-alpha))+tanalpha:(-cosalpha)=\=cosalphatanalpha-tanalpha:cosalpha=cosalphacdotfrac{sinalpha}{cosalpha}-frac{sinalpha}{cos^2alpha}=\=sinalphacdotleft(1-frac1{cos^2alpha}right)=-sinalphaleft(frac1{cos^2alpha}-1right)=-sinalphacdotfrac{1-cos^2alpha}{cos^2alpha}=\=-sinalphacdotfrac{sin^2alpha}{cos^2alpha}=-sinalphatan^2alpha$