11 . The coordinates of the points O , A , B , C and D are ( 0 , 0 , 0 ) , ( 0 , 9 , 0 ) , ( 0 , 9 , � 9 ) , ( 0 , 0 , � 9 ) and ( � 9 , 0 , 0 ) respectively . E is a point on the line segment BD such that CE
� BD .
( a ) Show that the coordinates of E are ( �3 , 6 , � 6 ) .
( b ) Find the obtuse angle between the plane ABD and the plane BCD .
( c ) F is a point on the positive x -axis such that the volume of the solid
FODABC is 783 . Find the value of DF .
[ 6 ]
[ 9 ]
[ 4 ]
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