1-cosa sina·sina/cosa =1-sin²a =cos²a
81=(3²)²)=9²
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1. 3x=π/2+πn, n∈Z
x=π/6+πn/3, n∈Z
2. x/2=-π/4+πn, n∈Z
x=-π/2+2πn, n∈Z
3. -4x=π/4+πn, n∈Z
x=-π/16+πn/4, n∈Z
4. 3x-π/6=π/6+πn, n∈Z
3x=π/3+πn, n∈Z
x=π/9+πn/3, n∈Z
5. π/6-2x=π-π/6+πn
-2x=2π/3+πn
x=-π/3+πn/2, n∈Z
Сosx(cosx+1/2sinx)=0
cosx=0
x=π/2+πk,k∈z
cosx+1/2sinx=0 /cosx
1+1/2tgx=0
tgx=-2
x=-arctg2+πk,k∈z
Ответ:x=6; y=1
Объяснение:x=5+y; y+5+y=7; 2y=2;
y=1; x=5+1; x=6