question_answer

The value of \[aa'+\,bb'+\,cc'\]being negative the origin will lie in the acute angle between the planes \[an+by+cz+d=0\] and \[a'x+b'y+c'z+d'=0\], if [MP PET 2003]

A)            \[a=a'=0\]                                 

B)            d and \[d'\]are of same sign

C)            d and \[d'\]are of opposite sign

D)            None of these