The combined equation of the lines is and that of the lines is . If the angle between and be , then the angle between and will be 

a) 

b) 
c) 
d) 
The combined equation of the lines is and that of the lines is . If the angle between and be , then the angle between and will be 

a) 

b) 
c) 
d) 
(d)
The combined equation of bisectors of angles between the lines of the first pair is
As these equations are the same, the two pairs are equally inclined to each other