400 + 320 = 720 ( т ) всего убрал
720 : 9 = 80 ( т ) убирал за 1 день
400 : 80 = 5 ( дней ) убирал с первого поля
320 : 80 = 4 ( дня ) убирал со второго поля
АB=BC,AC=a,<ABC=α,<SFO=<STO=<SHO=β
SF_|_AB,SE_|_BC,SH_|_AC
AH=CH=a/2
<ABH=<CBH=α/2
AB=BC=AH/cos<ABH=a/2cos(α/2)
BH=AH/tg<ABH=a/2tg(α/2)
BO=2/3*BH=a/3tg(α/2)
OH=1/3*DH=a/6tg(α/2)
FO=EO=DO*sin<ABH=asin(α/2)/3tg(α/2)=acos(α/2)/3
SF=SE=FO/cjs<SFO=acos(α/2)/cosβ
SH=OH/cos<SHO=a/(6tg(α/2)*cosβ)
Sп=2S(SBA)+S(SAC)+S(ABC)=2*1/2*AB*SF+1/2*AC*SH+1/2*AC*BHSS=a*a*cos(α/2)/(2cos(α/2)*cosβ)+a*a/(6tg(α/2*cosβ)+a*a/(4tg(α/2))=
=a²/(2cosβ)+a²/(6tg(α/2*cosβ)+a²/(4tg(α/2)=
<span>=a²/2*(1/cosβ+1/(6tg(α/2)*cosβ)+1/(4tg(α/2))</span>
0 = (5 - 5)*555
1 = 5 - (5*5 - 5)/5
5 = 5 + 55 - 55
6 = 5 + 55/55
7 = 5 + 5/5 + 5/5
15 = 5 + 5 + 5 + 5 - 5
17 = ???
20 = 5*5 - 5 + 5 - 5