1.四边相等=2cm
2.
连接BD
∵∠ABC=2∠BAD
BC//AD
∴∠ABC=2∠BAD=120°
∴∠BAD=60°
∴BD=2cm
连接AC交BD于点O
AO=√AB²-(BD/2)平方=√3cm(勾股定理)
∴AC=2√3cm
3.S=2×S△ABD=2×√3=2√3 cm²
1.四边相等=2cm
2.
连接BD
∵∠ABC=2∠BAD
BC//AD
∴∠ABC=2∠BAD=120°
∴∠BAD=60°
∴BD=2cm
连接AC交BD于点O
AO=√AB²-(BD/2)平方=√3cm(勾股定理)
∴AC=2√3cm
3.S=2×S△ABD=2×√3=2√3 cm²