The angle between the lines $x^2 + 4xy + y^2 = 0$ is ..... $^o$.

If $(a + 3b)(3a + b) = 4h^2$,then the angle between the lines represented by $ax^2 + 2hxy + by^2 = 0$ is.....$^o$

The combined equation of the two diameters of a circle which divide the circle into $4$ sectors is $ax^2+2hxy+by^2=0$. If the area of the bigger sector is $5$ times the area of the smaller sector,then $\frac{|a+b|}{\sqrt{(a-b)^2+4h^2}} = $

The measure of the acute angle between the lines given by the equation $3x^{2}-4\sqrt{3}xy+3y^{2}=0$ is (in $^{\circ}$)

The angle between the pair of straight lines $3y^2 - 8xy - 3x^2 - 29x + 3y - 18 = 0$ is (in $^{\circ}$)

The angle between the lines represented by $(\sin ^2 \alpha) y^2 - 2xy(\cos ^2 \alpha) + (\cos ^2 \alpha - 1) x^2 = 0$ is