1.A
2.D
3.22
4.13或√119
5.B
6.等腰
7.72° 72° 4
8.√7
9.∵DB=DC ∴∠DBC=∠C=29°∵∠ADB=∠DBC=∠C∴∠ADB=58°∵AB=AD∴∠ADB=58°∴∠A=64°
10.∵AD=AE ∴∠ADE=∠AED∴∠ADB=∠AEC 在△ABD和△ACE中,∵AD=AE ∠ADB=∠ACE BD=CE ∴△ABD≌△ACE(SAS)∴AB=AC
11.4.8
12.B
13.連結(jié)BC,∵AB=AC ∴∠ABC=∠ACB∵∠ABD=∠ACD∴∠CBD=∠BCD∴BD=CD
14.∵是Rt△∴8²+6²=100=10²∴另一條邊長為10 S1=8π S2=4.5π S3=12.5π S1+S2+S3=8π+4.5π+12.5π=25π
15.連結(jié)BC,在△ABC和△DCB中,∵∠A=∠D BD=AC BC=CB∴△ABC≌△DCB(Hl)∴AB=DC 在△ABO和△DCO中,∵AB=BD ∠C=∠D ∠AOB=∠DOC∴△ABD≌△DCO∴OB=OC
16.CD=3cm