X²-x-1=0
D=b²-4ac=-1²-4*1*(-1)=1+4=5
x1=(-b+√D)/2a= (-(-1)+√5)/2= (1+√5)/2
x2=(-b-√D)/2a= (1-√5)/2
Sin20cosa+sinacos20-sin20cosa+sinacos20=2*sinacos20°≈2*0, 93*sina=1,86*sina
T > 1
z < 20
4z < 80
- 4z > - 80
t - 4z > - 79
S = 180(n-2) = 180 * (12-2) = 1800
Ответ: 1800
<span>1+cos5x sin4x=cos4x sin5x</span>