X^2 + 2Y^2 = 36
3X^2 - 2Y^2 = - 20
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X^2 + 3X^2 + 2Y^2 - 2Y^2 = 36 - 20
4X^2 = 16
X^2 = 4
X1 = 2
X2 = - 2
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X^2 + 2Y^2 = 36
4 + 2Y^2 = 36
2Y^2 = 32
Y^2 = 16
Y1 = 4
Y2 = - 4
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Ответ ( 2 ; 4 ) ; ( - 2 ; - 4 )
Ctgt=cost/sint
sin(-t)=-sint
cos(2π-t)=cost
ctgt*sin(-t) + cos(2π-t)=cost*(-sint)/sint + cost=-cost+cost=0
1/sin²=1+ctg²a
1+ctg²a-1=ctg²a
ctg²a=ctg²a