慜>>226
梋尫掕棟傛傝丄
cos佢QPR=(3^2+5^2-6^2)/2񑧉 =-2/30
=-1/15
佢QPR=偼妏偼偩偐傜偁偵側傞偱偱偭 丅


掕棟傛傝丄


佢P=R=6/2x


3/x


ig n ^2 QRP佢

=1- 1/226 暥帤偟偰偆傑偔彂偗側偄偑丄壔偗x
=3亊15/併22424
524 併


/

224

14



2.006688亝r亝4.006688