if `1 / (ab') + 1 / (ba') = 0` , then lines ` x/ a + y / b =1` and `x / (b') + y / (a') = 1` are

Angle between the lines (x)/( a) + (y)/( b) and (x)/(a) - (y)/( b) = 1 is ….....

Show that the tangent of an angle between the lines (x)/(a) + (y)/( b) = 1 and (x)/( a) - (y)/( b) = 1 is (2 ab)/( a^(2) - b^(2) ) .

Prove that the diagonals of the parallelogram formed by the four lines : x/a +y/b=1,x/b+y/a= 1, x/a + y/b = -1 and x/b + y/a = -1 are at right angles .

The point of intersection of the lines x/a + y/b = 1 and x/b + y/a = 1 does not lie on the line

The point of intersection of the lines x/a+y/b =1 and x/b +y/a =1 lies on the line

Prove that the line through the point (x_(1) , y_(1)) and parallel to the line Ax + By + C =0 " is " A (x - x_(1)) + B (y - y_(1)) = 0 .

Prove that the line through the point (x_(1) , y_(1)) and parallel to the line Ax + By + C =0 " is " A (x - x_(1)) + B (y - y_(1)) = 0 .