Special Pairs of Angles 2

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Two Parallel Lines Intersected by a Transversal

In Chapter 159, we saw that one of the ways, 3 lines can be placed on a plane surface is that of 2 lines being parallel with the 3rdline intersecting both of them. The intersecting line is called a Transversal. In this formation we can study various angles which occur in pairs. Some of these pairs also have interesting properties.

It would be easy if the diagram given below is referred to. A total of 8 angles, which can be grouped into 4 pairs A, B, C, D, E, F, G &amp; H.



Though these names &amp; their properties seem confusing, they can all be visually derived from just 2 properties –

There is no need to memorise them.
 * 1) Vertically opposite angles are equal and
 * 2) Internal angles on the same side of the transversal are supplementary

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