Question

等腰梯形ABCD中,AB=DC,对角线AC平分∠BAD,梯形的周长为4.5cm,下底AB=1.5cm,求上底CD的周长.

Answer 1

∵AD∥BC,

∴∠DAC=∠ACB,

又∵∠DCA=∠ACB,

∴∠DAC=∠DCA,

∴AD=CD,

又∵AB=CD,

∴AB=CD=AD,

又∵AB+BC+CD+DA=4.5,BC=1.5,

∴上底=CD=1 CM