Find the acute angle between the lines x - `sqrt3` y = 1 and `sqrt3` x -y = 4

Find the angle between the lines x-sqrt 3y=1 and sqrt 3x-y=1 .

Find the distance between the parallel lines 3x-4y+9=0 and 6x-8y-15=0 .

Find the angle between the pari of lines given by (x -1)/(2) = (y -2)/(3) = (z -3)/(4) and (x -3)/(4) = (y -2)/(3) = (z -1)/(2).

Find the value of m for which the lines 4x -3y - 1 = 0, 3x - 4y + 1 = 0 and mx - 7y + 3 = 0 are concurrent.

Find the equation of the tangents to the circle x ^2 + y ^2 - 2x - 4y - 4 = 0 which are perpendicular to the line 3x - 4y - 1 = 0