∵A1B、A1C分别平分∠ABC和∠ACD，∴∠ACD=2∠A1CD，∠ABC=2∠A1BC，而∠A1CD=∠A1+∠A1BC，∠ACD=∠ABC+∠A，∴∠A=2∠A1同理可得∠A1=2∠A2，即∠A=22∠A2，所以∠A=25∠A5，而∠A=96°，∴∠A5=96°÷32=3°．
