设c = (x ,y) ,bc = oc - ob = (x+2 ,y-4 ) ,oc =(x ,y),
oa=(1.3),ob = (-2,4)
oc垂直ob oc*ob = 0 ,-2 *x+ 4* y =0
bc平行oa (x+ 2)/(y-4) =1/3
解得 x= -4 ,y = -2
即 c=(-4 ,-2)
设c = (x ,y) ,bc = oc - ob = (x+2 ,y-4 ) ,oc =(x ,y),
oa=(1.3),ob = (-2,4)
oc垂直ob oc*ob = 0 ,-2 *x+ 4* y =0
bc平行oa (x+ 2)/(y-4) =1/3
解得 x= -4 ,y = -2
即 c=(-4 ,-2)