csat-suneung 2007 Q21

csat-suneung · South-Korea · csat__math-science 4 marks
In coordinate space, let B be the foot of the perpendicular from the point $\mathrm { A } ( 3,6,0 )$ to the plane $\sqrt { 3 } y - z = 0$. Find the value of $\overrightarrow { \mathrm { OA } } \cdot \overrightarrow { \mathrm { OB } }$. (Here, O is the origin.) [4 points]
In coordinate space, let B be the foot of the perpendicular from the point $\mathrm { A } ( 3,6,0 )$ to the plane $\sqrt { 3 } y - z = 0$. Find the value of $\overrightarrow { \mathrm { OA } } \cdot \overrightarrow { \mathrm { OB } }$. (Here, O is the origin.) [4 points]