1) 1 - Sin² y = Cos²y
2) tg 2b - Cos 2b/-Сos 2b= tg 2b +1
1+sin(π+α)*cos(3π/2+α)=1+(-sin(α))*sin(α)=1-sin²α=cos²α
5x+5=6+5x-15
10x=-4
(-4)-является корнем уравнения
A3+a6=3,a7=a2-15,a1=?,a2=?
a3=a1+2d, a6=a1+5d, a1+2d+a1+5d=3,2a1+7d=3
a2=a1+d, a7=a1+6d, a1+6d=a1+d-15, 5d=-15, d=-3
2a1+7d=3, 2a1=3-7d, 2a1=3+21=24, a1=12
a1=12,a2=9
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a3=6, a6=-3, a3+a6=3,
a7=-6,a2=9, -6=9-15
S4=b1*(q^7-1)/(q-1)
b1*(128-1)/(2-1)=635
b1=635/127
b1=5