∵ab=ad∴∠abd=∠adb∵ad//bc∴∠dbc=∠adb∵ad//bc,ab=dc=ad∴梯形abcd为等腰梯形∠cba=∠dcb=2∠adb∵bd垂直cd∴∠bad=∠adc=90°+∠adb∵∠cba+∠dcb+∠bad+∠adc=360°2∠adb+2∠adb+90°+∠adb+90°+∠adb=360...