40/60 = две третьих (2/3) часа
4sin^2 x - 2 sin x * cos x - sin^2 x - cos ^2 x = 0 ( : cos^2 x)
4 tg^2x - 2 tg x - tg x - 1 = 0
tg x = l, x ≠ p/2 + pn, n ∈ Z
4l^2 - 3 l - 1 = 0
D= 9+ 16= 25;
x(1,2) = 3+5/8 = 1; 3-5/8 = -1/2;
tg x = 1;
x = p/4 + pm, m ∈ Z.
tg x = 1/2
x = arctg 1/2 + pk, k ∈ Z.
Ответ:
2x>15
x>15/2
- 3x>-12
x<4
<em>Оцените</em><em> </em><em>если</em><em> </em><em>не сложно</em><em>.</em><em> </em>
<span>127-y=357-85 85+65=150
</span>357-85=272 150-125=25
272-127=145 у=25
у=145 <span>125+25-85=65
</span>127+145=357-85
5 х 14 - 4 х 3 <span>=70-12=58 </span>