Sin(60°+a)sin(60°-a) = (1/2)*[cos(60° + α - 60° + α<span>) -
- cos(</span>60° + α + 60° - α)] = (1/2)*[cos2α - cos(120°)] =
<span>= (1/2)*[cos2α + cos(60°)] = (1/2)*[cos2α + 1/2)] = (1/2)*cos2α + 1/4</span>
{22x+17y=49 ;×26
{31x-26y=119 ;×17
{572x+442y=1274
+
{527x-442y=2023
-----------------------------
1099x=3297
x=3
22x+17y=49
66+17y=49
17y=49-66
17y=-17
y=-1
OTBET (3;-1)
X = arc tg(-1/√3) + πk , k ∈Z
x = - π/6 + πk , k∈Z
1. (a-1)(2a-b)
2. (b-2)(a-3c)
3. (a+2)(c-d)
4. (2w-y)(2x+3z)
A)y=-0,2x+4 не пересечётся с графиком функцииy=-x/5
b)y=7x <span>параллелен прямой y=7x-12</span>