The angle between the pair of lines x2+4xy+2y2=0 is

If θ is acute angle between pair of lines represented by the equation ax2+2hxy+by2=0 then  cosθ=a+b(a−b)2+(2h)2For the equation x2+4xy+2y2=0, a=1,2h=4,b=2Hence, cosθ=31+16=317Therefore,θ=cos−1317