The angle between the lines $2x - y + 3 = 0$ and $x + 2y + 3 = 0$ is ........... $^\circ$

The lines $a_1x + b_1y + c_1 = 0$ and $a_2x + b_2y + c_2 = 0$ are perpendicular to each other,if

Show that the equation of the line passing through the origin and making an angle $\theta$ with the line $y=mx+c$ is $\frac{y}{x}=\frac{m \pm \tan \theta}{1 \mp m \tan \theta}$.

What is the angle in degrees between the lines $x = 9$ and $x - \sqrt{3}y + 7 = 0$?

If the angle between the lines is $\frac{\pi}{4}$ and the slope of one of the lines is $\frac{1}{2}$,then the slope of the other line is

If the lines $y = 3x + 1$ and $2y = x + 3$ are equally inclined to the line $y = mx + 4$,then $m =$ ?