平行四边形abcd的对角线ac,bd交于点o,ac垂直ab,ab=2,且ac:bd=2:3（1）求ac的长平行四边形abcd的对角线ac,bd互相平分oa=ob=0.5ab,oc=od=0.5cdac:bd=2:3oa:ob=2:3ac垂直ab,ab=2,oa^2+ab^2=ob^2oa=0.8根号5,ob=1.2根号5...