Find the angle between the lines -x+y-2=0, 6x-6y+1=0
There is no angle between the lines. They are parallel with each other.
Taking the 1st line.
-x+y-2=0 is equivalent to,
x - y = -2 (multiply the eqn by -1 and rearrange)
6x - 6y = -12 (multiply by 6)
And the 2nd eqn is,
6x - 6y = -1
i.e. both lines are parrallel with each other, but simply have different y-intercepts.