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X=3x 12=4x x=3 4) эквивалентно 5x+1<19 5x<18 x<3,6
<span>(tg(п+a)+1)(-ctga+1)/(-tga+1)(ctga+1)=(tga+1)(-ctga+1)(-tga+1)(ctga+1)=(-tga*ctga+tga-ctga+1)/(-tgactga-tga+ctga+1)=(tga-ctga)/(ctga-tga)=-(ctga-tga)/(ctga-tga)=-1</span>