如图,在△ABC中,AB=AC,∠A=36°,BD平分∠ABC交AC于点D,若AC=2,求AD的长.

问题描述:

如图,在△ABC中,AB=AC,∠A=36°,BD平分∠ABC交AC于点D,若AC=2,求AD的长.

设AD=x,∵在△ABC中,AB=AC,∠A=36°,∴∠ABC=∠C=72°,∵BD平分∠ABC,∴∠ABD=∠CDB=36°,∴∠A=∠ABD,∠BDC=∠A+∠ABD=72°=∠C,∴AD=BD=BC=x,∵AC=2,∴AB=2,CD=AC-AD=2-x,∵∠DBC=∠A,∠C=∠C,∴△...