<span>Sin^2х-9sin x cos x +3cos^2x=1
</span><span>Sin</span>²<span>х-9sin x cos x +3cos</span>²<span>x= Sin</span>²x + Cos²x
<span>2Cos</span>²x -9SinxCosx = 0
<span>Cosx(2Cosx -9Sinx) = 0
Cosx = 0 или 2Cosx - 9Sinx = 0|: Cosx
x = </span>π/2 + πk , k ∈Z 2 - 9tgx = 0 <span>
</span> tgx = 2/9
x = arctg(2/9) + πn , n ∈ Z
2sinx≥-√2
sinx≥-√2/2
-П/4+2Пn,nєZ;
5П/4+2Пk,kєZ