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)=
=a²/2*(1/cosβ+1/(6tg(α/2)*cosβ)+1/(4tg(α/2))
1) 37,8=37 8/10=37 4/5 см - периметр
2) 37 4/5*2/9=189/5*2/9=21/5*2/1=42/5=8 2/5 см - 1 сторона
3) 37 4/5 * 3/7=189/5 *3/7=27/5*3/1=81/5=16 1/5 см - 2 сторона
4) 8 2/5 + 16 1/5=24 3/5 см - сумма длин 1 и 2 стороны
5) 37 4/5-24 3/5=13+1/5=13 1/5 см -3 сторона
37-24=13
4/5-3/5=1/5
1. 30,8+27,4=58,2
2, 31,64-12,24=19,4
3. 58,2*0,9=52,38
4. 19,4*1,2=23,28
5. 52,38/23,28=2,25