求圆台的表面积,已知圆台的上圆直径为30cm,下半圆直径为150cm,高是100cm,其他没有了,求此圆台的表面积我要裁

补充为圆锥,见附图:
DA:CG=OA:OG,
(DA-CG):CG=(OA-OG):OG,
(DA-CG):CG=GA:OG,
(75-15):15=100:OG,
OG=25(cm),
OA=OG+GA=25+100=125(cm);
OC=√(OG²+CG²)=√(25²+15²)=5√(34)(cm),[=29.15]
OD=√(DA²+OA²)=√(75²+125²)=25√(34)(cm);[=145.77]
展开为扇形,
扇形ODD'的面积=弧长DD'*OD/2
=2π*AD*OD/2
=3.14*75*25√(34)
=34347.14(cm²);
扇形OCC'的面积=弧长CC'*OC/2
=2π*GC*OC/2
=3.14*15*5√(34)
=1373.89(cm²);
侧面积=扇形ODD'的面积-扇形OCC'的面积
=34347.14-1373.89
=32973.26(cm²);
表面积=上底面面积+侧面积+下底面面积
=π*CG²+32973.26+π*DA²
=3.14*15²+32973.26+3.14*75²
=51351.57(cm²);
裁板见附图,
PF=CD+上圆直径+下圆直径
=OD-OC+30+150
=25√(34)-5√(34)+180
=145.77-29.15+180
=296.62(cm);
EF=2*OD=2*25√(34)=291.55(cm);
长方形板长=PF=296.62cm,宽=EF=291.55cm;