SinB=AH/AB=√21/5
cosB=√1-sin²B=√1-21/25=√4/25=2/25
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2). О.Д.З. y+3≠<span>0, у≠ -3. y^2=</span><span> y; y^2-y=</span>0; у(у-1)=0; у=0, у=1 Ответ: 0;1</span>
<span>3). О.Д.З. 7-x≠0, x≠7. 12=x(7-x); 12=7х-х^2; х^2-7x+12=0; Д</span>
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