<span>cos(π/5)*cos(2π/5)</span><span><span>=<span><span>sin(π/5)*cos(π/5)*cos(2π/5)/</span><span>sin(π/5)</span></span></span><span>=<span><span>sin(2π/5)*cos(2π/5)/</span><span>2sin(π/5)</span></span></span><span>=<span><span>sin(4π/5)/</span><span>4sin(π/5)</span></span></span><span>=<span>1/4</span></span></span>
x=p-r
y=q-s
Система 2x+y=24; -x+2y=26
удваиваем второе и складываем с первым
5y=26*2+24
y=76/5
подставлю в первое
2x+76/5=24
2x=24-15.2=8.8
x=4.4 (=22/5)
p-q=22/5
q-s=76/5
Он дцп ребзи , расходимся...
(m-6)(m+6)=m^2-6^2=m²-36
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