tolong pakai caranya

BC=√(28²+21²)=35 cm
OD=OE=AD=AE=r
(tambahkan garis dr O tegak lurus BC, kita namakan OF)
CE=CF=21-r
BD=BF=28-r

CF+BF=BC
21-r+28-r=35
49-2r=35
2r=14 mk r=7 cm
a) jd OD=r=7 cm
b) BD=28-7=21 cm
c) OB=√(7²+21²)=7√10 cm
d) CE=21-7=14 cm
Luas COE=½×7×14=49 cm²