<span> cos2t-cos4t-cos6t+cos8t=(cos2t+cos8t)-(cos 4t+cos6t)=</span>
<span>=2cos(2t+8t)/2*cos(2t-8t)/2-2cos(4t+6t)/2*cos(4t-6t)/2=</span>
<span>=2cos5t*cos3t-2cos5t*cost=2cos5t(cos3t-cost)=</span>
<span>=-4cos5t*sin(3t+t)/2*sin(3t-t)/2=-4cos5t*sin2t*sint</span>
1+1+3+2=7 всього
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1. log [4] (2.56×6.25)=log [4] 16=2
2 169^(log [sqrt (13)] 2)=13^(2×2×log [13] 2)=2^4=16
3 log [0.04] (5×0.2^(1/4))=1/2×log [0.2](0.2^(-3/4))=1/2×(-3/4)=-3/8
4 log[2.5] log [27] (3×root (3;5)))= log [2.5] 1/3 log [3] (3^(6/5))=log [5/2] (1/3×6/5)=log [5/2] 2/5=-1
5 log[a](a^3×b^(1/8))=3×1/8 log [a] b =3/8 log [a] a^(4/5)=3/8×4/5=3/10=0.3
1)48:3*1=16(км)-1 день
2)16+4=20(км)-2 день
3)20:4=5(км)-3день
4)48-16-20-5=7(км)
Ответ: туристы преодолели в четвертый день 7 км
4+9х=1
9х=1-4
9х=-3
х=-3:9
х=-1/3
Проверка:
4+9·(-1/3)=1
4+(-3)=1
1=1
2х-5=-10
2х=-10+5
2х=-5
х=-5:2
х=-2 1/2=-2,5
Проверка:
2·(-2 1/2)-5=-10
-5-5=-10
-10=-10