已知sin二分之阿拉法=五分之三,cos二分之阿拉法=负五分之四,则阿拉法角终边所在的象限为

问题描述:

已知sin二分之阿拉法=五分之三,cos二分之阿拉法=负五分之四,则阿拉法角终边所在的象限为

sina/2=3/5>0
cosa/2=-4/5由题2kπ+3π/4