Cos2α-cos6α=2sin4αsin2α=2*2sin2αcos2αsin2α=4sin²2αcos2α=4*(2sinαcosα)²*(cos²α-sin²α)=16sin²αcos²α*(cos²α-sin²α)=(cos²α=1/3⇒sin²α=1-cos²α=1- 1/3 = 2/3)=
=16*2/3*1/3*(1/3 - 2/3)= - (16*2*1*1)/(3*3*3)= -32/27= - 1 целая 5/27
1
8x²-160x+800-11x²-110x-275+3x²+170x-1600=0
-100x=1075
x=-10,75
2
40+20x+2,5x²+175-7x²-295+4,5x²=0
20x=80
x=4
Эм пять цэлых пять десятых