Ответы на вопрос:
1sin^2(a+b)+cos^2(a-b)-sin2a sin2b= =(1-cos(2a+2b))/2+(1+cos(2a-2b))/2-sin2asin2b= =1/2-1/2cos2acos2b+1/2sin2asin2b+1/2+1/2cos2acos2b+1/2sin2asin2b- sin2asin2b=2 2 а) sin(179°+x) cos x -cos(179°+x) sin x> 0 sin(179+x-x)> 0 sin179> 0 x∈(-∞; ∞) б)x^2-2x cos6,5 cos0,5+cos6 cos7< 0 cos6,5cos0,5=1/2(cos(6,5-0,5)+cos(6,5+0,5))=1/2(cos6+cos7) x²-2x*1/2(cos6+cos7)+cos6cos7< 0 x²-x(cos6+cos7)+cos6cos7< 0 x1+x2=cos6+cos7 u x1*x2=cos6cos7 x1=cos6 u x2=cos7 x∈(cos6; cos7)
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