=-9,8+(-3,2)+17+13=-13+30=17
1)-3sina+1/5sina=-2 4/5sinπ/2=-2 4/5*1=-2 4/5
2)cos(5π/6-π/6)=cos2π/3=-1/2
3)cos2x/cos²x=(sinx+cosx)/cosx
cosx≠0
cos2x=sinxcosx+cos²x
cos²x-sin²x-sinxcosx-cos²x=0
sin²x+sinxcosx=0/cos²x
tg²x+tgx=0
tgx(tgx+1)=0
tgx=0⇒x=πn
tgx=-1⇒x=-π/4+πn
Координаты вершины параболы : (- 2 ; 10)
<span>Х</span>² <span>- (11х+2)/6 = 0
6x</span>² - 11x - 2 = 0
<span>D = 121 + 4*6*2 = 169
x</span>₁ = (11 - 13)/12
<span>x</span>₁ = - 1/6
<span>x</span>₂ = (11 + 13)/12
<span>x</span>₂ = 24/12
<span>x</span>₂ = 2<span>
</span>