<span>2sin^2 x - 10cos 2x = 9sin 2x +10
</span>2Sin²x - 10(Cos ²x - Sin²x) <span>= 9*2Sin xCosx +10*1
</span>2Sin²x - 10Cos ²x +10 Sin²x = 9*2Sin xCosx +10*(Sin²x + Cos²x)
2Sin²x - 10Cos ²x +10 Sin²x = 9*2Sin xCosx +10Sin<span>²x + 10Cos²x
</span>2Sin²x - 18SinxCosx -20Cos²x = 0
Sin²x - 9SinxCosx -10Cos²x = 0 | : Cos²x ≠0
tg²x - 9tgx -10 = 0
По т. Виета
tgx = 10 tgx = -1
x = arctg10 + πk , k ∈ Z x = -π/4 + πn , n ∈Z
(x-3)²+(3-x)(x+3)=(x+2)²-x²
x²-6x+9+9-x²=x²+4x+4-x²
-6x+18=4x+4
4x+6x=18-4
10x=14
x=14:10=1,4