The direction cosines of the normal to the plane `5y+4=0` are

Options

A. `0,-4/5,0`
B. `0,1,0`
C. `0,-1,0`
D. none of these

Answer

c

Explanation

`5y+4=0 rArr -5y=4 rArr -y=4/5 rArr 0x-1.y+0.z=4/5`.
D.r,s of the normal to this plane are `0,-1.y+0.z=4/5`.
D.r.'s of the normal to this plane are `0,-1,0` and `sqrt(0^(2)+(-1)^(2)+0^(2))=sqrt(1)=-1`.
`therefore` d.c's of the normal to this given plane are `0,-1,0`.