[Junior high school math problems1(supplemented by100)]

(1) Do high:

Do AE, DF⊥BC, drop E and F.

∠B=30 degrees, ∠D= 120 degrees, ∠C=60 degrees.

CD=5cm, then CF=2.5, DF=2.5* radical number 3, EF=AD=3, BE=AE* radical number 3=DF* radical number 3=7.5, AB=2DF=5* radical number 3.

Circumference = ab+be+ef+fc+CD+ad = 21+5 * root number 3.

(2) in e, do DE//AB and BC, ∠C=60 degrees, ∠DEC=30 degrees, and AB=DE.

=CD* radical number 3=5* radical number 3, BE=AD=3, EC=2DC= 10.

Circumference =AB+BE+EC+CD+AD=2 1+5* root number 3.

③ Extend the intersection time of BA and CD with E.

∠EDA=60 degrees, ∠EAD=30 degrees.

ED=AD/2= 1.5, EA=ED* radical number 3= 1.5* radical number 3.

ED:EC = EA:EB = AD:BC = 1.5:( 1.5+5)= 3: 13，

The solution is BC= 13, EB= 6.5* radical number 3, AB=EB-EA=5* radical number 3.

Circumference =AB+BC+CD+DA=2 1+5* root number 3.