Ответы и объяснения

2013-02-27T17:19:28+04:00

cos ^- 4 x/2 * (2sin^4 x/2 -1) =2

2sin^4 x/2 -1=2cos^4 x/2

2sin^4 x/2 -2cos^4 x/2 =1

2(sin^2 x/2 +cos^2 x/2)(sin^2 x/2-cos^2 x/2)=1

2(sin^2 x/2-cos^2 x/2)=1

-2cosx=1

cosx=-1/2  x=+-arccos(1/2)+2pik  x=+-pi/6+2pik (k=0,1,2,3,4,5,...)