If $3x + 4y - 5 = 0$ and $4x + ky - 8 = 0$ are two parallel lines,find the value of $k$.

The lines $y = 2x$ and $x = -2y$ are

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 $\alpha^2 + 2\beta =$

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

The obtuse angle between the lines $y = -2$ and $y = x + 2$ is .....$^o$

Find the angles between the lines $\sqrt{3}x + y = 1$ and $x + \sqrt{3}y = 1$.