► The sum of all the angles round a point is equal to 360º.
► If two lines intersect, then the vertically opposite angles are equal.
Angle a = angle b (vertically opposite angle)
► If a transversal intersects two parallel lines, then each pair of corresponding angles are equal.
Other facts :
1. Linear pair :
a + b = 180º
2. Vertical opposite angles:
a = c & b = d e = g & f = h
3. Alternate angles:
c = e, d = f
4. Sum of Interior angle is always 180º:
c + f = d + e = 180º
