Question

在四边形ABCD中,AD=8,CD=6,AB=13,角ADC=90度,且AB向量*AC向量=50

Answer 1

设:∠BAC=P,∠CAD=QAC=√[6²+8²]=10,∴sinQ=6/10=3/5,cosQ=8/10=4/5cosP=AB向量*AC向量/(AB*AC)=50/130=5/13===>sinP=√[1-(5/13)²]=12/13∴sin角BAD=sin(P+Q)=sinPcosQ+cosPsinQ=(12/13)(4/5)+(5/13...