4) = sin (5x+3x) =sin8x
5) = cos (5x+3x) =cos 8x
6) = sin(7x+4x) = sin11x
7) = cos (2x+12x) =cos 14x
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8)sin (5π/6-a)-1/2cosa = sin5π/6 cosa - cos5π/6 sina -1/2cosa=0.5cosa-(-√3/2sina)-1/2cosa=1/2cosa+√3/2sina-1/2 cosa=√3/2sina
√3/2sina+cos(a-5π/3)= √3/2sina+cosa cos 5π/3 + sina sin5π/3=
=1/2cosa
подставлено
cos 5π/3 =cos300 = 1/2 sin300=-√3/2
по формулам приведения cos300 = cos(270+30)=sin30
sin (300)=sin(270+30)=-cos30
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