(0,8x+y)*(y-0,8x)= -0,64x^2+y^2. Ответ: -0,64x^2+y^2.
2x+2y=104; |:2
<span>3y - 2x=18
x+y= 52
3y - 2x = 18
x= 52 - y
3y - 2(52 - y) = 18
3y - 104 +2y = 18
5y= 122
y= 24,4
x= 27,6
Ответ: (27,6; 24,4).</span>
Arccos(cos37π/3)=arccos(cos(12π+π/3))=arccos(cosπ/3)=arccos(1/2)=π/3
Cos(x)=√1-(2/5)²=√(1-4/25)=√(21/25)=√(21) /5
tg(x)=sin(x)/cos(x)= 2/5 : √(21)/5 =2/5 *5/√(21)= 2/√(21)