Question

Даю 30 баллов, пожалуйста помогите Докажите тождество
Номер 349 в)

Answer 1

$cos(pi-alpha)=-cos(alpha)\cos({piover2}+alpha)=-sin(alpha)\tg({3piover2}+alpha)=-ctg(alpha)\sin^2alpha+cos^2alpha=1\ctgalpha={cosalphaover sinalpha}\\{1-cos^2alphaover1-sin^2alpha}-{1over ctg^2alpha}={sin^2alphaover cos^2alpha}-{1over{cos^2alphaoversin^2alpha}}={sin^2alphaover cos^2alpha}-{sin^2alphaover cos^2alpha}=0$