The acute angle between the lines $x-y=0$ and $y=0$ is

The angle between the straight lines $3x + 4y + 9 = 0$ and $x - 7y - 22 = 0$ is

If straight lines $\alpha^2x + \alpha y = 9$ and $3x + 2y = 5$ are perpendicular,then the value of $\alpha$ is

If $\alpha, \beta$ $(\alpha > \beta)$ are two values of $k$ such that the equations $2x + (3 - 2k)y + (2k + 1) = 0$ and $kx + (k - 1)y - 4 = 0$ represent two perpendicular lines,then $\alpha^2 + 2\beta =$

The distance between the two points $A$ and $A'$ which lie on $y = 2$ such that both the line segments $AB$ and $A'B$ (where $B$ is the point $(2, 3)$) subtend an angle $\frac{\pi}{4}$ at the origin,is equal to

The angle between the lines $x - \sqrt{3}y + 5 = 0$ and the $y$-axis is ....$^o$