☼ Parallel  Lines  :   Two straight lines in the same plane are said to be parallel, if they do not intersect in the entire plane. We can say that distance between any two points on two parallel lines is the same.

Let a transversal (cutting line)  l  cut two parallel lines m and n, then we have the following  properties :

■ Corresponding Angles ( All the images of F )  :   If  line l is a transversal of lines m and n, then there are following four pairs of corresponding angles are possible.

Note

 (i) There are four pairs of corresponding angles, if line  l  is a transversal of two lines m and n.

(ii)  m║n,  and  l  is a transversal of  m and n    corresponding angles are

equal.

i.e.        m d  =  m h,  m c  =  m g,  m b  =  m f,   m a  =  m e.

■ Alternate Angles ( All the images of Z )  :   If  line l is a transversal of lines m and n, then there are following two pairs of alternate angles are possible.

Note

(i) There are two pairs of alternate angles, if line  l  is a transversal of two lines m and n.

(ii) m║n,  and  l  is a transversal of m and n    alternate angles  are  equal.

i.e.        m c  =  m f,  m d  =  m e

■ Interior Angles ( All the images of C )  :   If  line l is a transversal of lines m and n, then there are following two pairs of interior angles are possible.

Note

 (i) here are two pairs of   interior angles, if line  l  is a transversal of two lines m and n.

(ii)  m║n,  and  l  is a transversal of  m and n    interior angles are supplementary.

i.e.        m d  +  m f   =  180^o,  m c  +  m e   =  180 ^o

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