<span>
x=2pi/3+2 piN,n э Z
x=4pi/3+2piN. nэZ</span>
1). 7 1/6-6=1 1/6; 2). 1/3-1/7=7/21-3/21=4/21; 3). 1 1/6*4/21=7/6*4/21=28/126.
Sin(-240°) = -sin240° = - sin(180 + 60) = sin60° = √3/2
cos(-240°) = cos240° = cos(180 + 60) = -cos60° = 1/2
tan(-240°) = -tan240° = -tan(180+60) = -tan60° = -√3
cot(-240°) = -cot240° = -cot(180+60) = -cot60° = -1/√3
4. y=2x+2
2*(-10)+2=-18
-20+2=-18
-18=-18
График проходит через эту точку
A₅+a₇-a₁₂=-9 a₁+4d+a₁+6d-a₁-11d=-9 a₁-d=-9 a₁=d-9
a₃+a₂₀=74 a₁+2d+a₁+19d=74 2a₁+21d=74 2(d-9)+21d=74
2d-18+21d=74
23d=92
d=4 ⇒
a₁=4-9=-5
S₁₆=(2a₁+(n-1)d)*n/2=(2*(-5)+15*4)*16/2=50*8=400.