⑴.L→AB（用规取）→同半径⊙A.⊙B各两个→半径EF得K,半径HG得R→
→连AK,BR.交于C.⊿ABC为所求.
⑵L→同半径两圆交于K,T→连KT交L于C→C为心TK上截CA→A为心AB为半径作弧
交L于B→连AB.⊿ABC为所求.