А) -y = 2,5
y = 2,5 : (-1) = - 2,5
б) -х = -4,8
х = (-4,8) : (-1) = 4,8
г) |y| = 8
При y меньше 0 - y = -8
при y больше 0 - y = 8
Решение
<span>Ctg a= - 7/24 , 450<a<540
ctg</span>²<span>a + 1 = 1/sin</span>²a
<span>sin</span>²a = 1 / (ctg²a + 1)
<span>sin</span>²a = 1 / [(-7/24)² + 1] = 1 / [(49/576) + 1] = 576 / 625
sina = 24/25
<span>cosx = - </span>√(1 - sin²a) = - √(1 - 576/625) = - √49/625 = - 7/25
<span>sin</span>²(a/2) = (1 - cosa)/2 = (1 + 7/25)/2 = 32/(25*2) = 16/25
<span>sin(a/2) = 4/5
</span>
2x-15-32x^2=3x*(<span>2x-3 4x^2-9 2x+3);</span>
=-13,2+32с+4,8с+5,2=36,8с-8