-3x^2+6x-1+10+2x*(x-5)+7x^2=3
-3x^2+6x-1+10+2x^2-10x+ 7x^2=3
6x^2-4x+9=3
(-17tg4⁰ -2tg176⁰)/(4ctg274⁰-ctg94⁰)=
=(-17tg4⁰-2tg(180⁰-4⁰)/(4ctg(270⁰+4⁰)-ctg(90⁰+4⁰)=
=(-17tg4⁰+2tg4⁰)/(4tg4⁰-tg4⁰)=(-15tg4⁰)/3tg4⁰=-5;
1) x больше 3
2) х меньше -2
3) х меньше -8
4) х меньше -7\20
5) х больше 0,1
6) х меньше -0,028
1)sin15°=sin(45-30)=sin45*cos30-cos45*sin30=√2/2(sin45)*√3/2(cos30)-√2/2(cos45)*1/2(sin30)=√6/4-√2/4=(√6-√2)/4
sin75°=sin(45+30)=sin45*cos30+cos45*sin30=√2/2(sin45)*√3/2(cos30)+√2/2(cos45)*1/2(sin30)=√6/4+√2/4=(√6+√2)/4
(√6-√2)/4-(√6+√2)/4=(√6-√2-√6-√2)/4=-2√2/4=-√2/2
2)cos15°+cos165°=
cos15°=cos(45-30)=cos45*cos30-sin45*sin30=√2/2(cos45)*√3/2(cos30)-√2/2(sin45)*1/2(sin30)=√6/4-√2/4=(√6-√2)/4
cos165=cos(90+75)=-sin75=-sin(45+30)=-(sin45*cos30+cos45*sin30)=-(√2/2(sin45)*√3/2(cos30)+√2/2(cos45)*1/2(sin30))=-(√6/4+√2/4)=(-√6-√2)/4
(√6-√2)/4+(-√6-√2)/4=(√6-√2-√6-√2)/4=-2√2/4=-√2/2
3)