已知在平面直角坐标系中,o为坐标原点 点a(-3,-4)b(5,-12)
AB=(5-(-3),-12-(-4))=(8,-8)|AB|=根号(8^2+(-8)^2)=8根号2
(2)OC=OA+OB=(-3,-4)+(5,-12)=(2,-16)
OD=(-3,-4)-(5,-12)=(-8,8)
(3)OA*OB=(-3,4)*(5,-12)=-3*5+4(-12)=-15-48=-63
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