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

The equations of the two straight lines passing through the point $(3, 2)$ and making an angle of $45^{\circ}$ with the line $x - 2y = 3$ are:

If the straight line $2x - 3y + 17 = 0$ is perpendicular to the line passing through the points $(7, 17)$ and $(15, \beta)$,then $\beta$ equals:

The equation of a straight line passing through the point $(1, 2)$ and inclined at $45^{\circ}$ to the line $y = 2x + 1$ is

The angle between the lines $y - x + 5 = 0$ and $\sqrt{3}x - y + 7 = 0$ is: (in $^o$)