類題 2) 設=(2,1,1), b=(x,2,-4),若與D之夾角為120°,則x=
9
中
x-1 L-AX + 4 = V bx E120
ai 5-1a1151 cos/20°
ă e = 2x+2-4 2X-2 = 56 58720 x - 72
2x
x2 2 47-4=JbXF 10 x
= 2X-2
lal-Jattl=56
&B 16+16=32X = 6XF 120 6x +10X12X
)
1 tl = 2 3 4+16 JX720
10X²32X-10q=0
b sx ²16X-5 2-0
Ų (x + 2) 151-260, X--2012
(
441=
X +
50-74
