Unity5 UI Different Screen Resolution and 2D Line problem

I have 3 POINTS in V shape. POINT_A, POINT_MID and POINT_B. POINT_MID is at centre of POINT_A and POINT_B.

I want to draw TWO lines from POINT_A to POINT_MID and POINT_B to POINT_MID.

I am using the following code to draw line.

 Vector3 differenceVector = endB- endA;
  
  imageRectTransform.sizeDelta = new Vector2( differenceVector.magnitude, lineWidth);
  imageRectTransfom.pivot = new Vector2(0, 0.5f);
  imageRectTransform.position = endA;
  float angle = Mathf.Atan2(differenceVector.y, differenceVector.x) * Mathf.Rad2Deg;
  imageRectTransform.Rotation = Quaternion.Euler(0,0, angle);

In the new UI I am using the reference screen resolution as 800x480. The problem is that if the screen resolution is less than 800x480; there is a gap between points. If the resolution is more than 800x480 then the lines are crossing each other at POINT_MID.

Can anyone help me out to resolve the problem?