В 6.......................................
<span>cos(x-5/(pi2))=cos(х)cos(5/(pi2))+sin(х)sin(5/(pi2))= sinx </span>
<span>если у вас написано 5pi/2 то cos(5pi/2)=0 </span>
<span>sin(5pi/2)=1 </span>
<span>cos(2x)=1-2sin^2(x) </span>
<span>1-2sin^2(x)-sinx-1=0 </span>
<span>sinx(2sinx+1)=0 </span>
<span>sinx=0, </span>
<span>x= n pi </span>
<span>и </span>
<span>sinх= -0.5, </span>
<span>x= -pi/6+2pi n </span>
<span>x= -5pi/ 6+2pi n </span>
<span>проверьте</span>
(10х15000 + 12х24000 + 15х20000 + 13х30000) : 50= (150000+288000+300000+390000):50= 1128000:50=22560
Ответ: (4, 2) ( . ) ( . )