**Parallel Straight Line: **

Definition: Lying in the same plane , two straight lines which do not meet are called parallel lines.

Some Corollary for parallel straight line:

* *1.When a transversal cuts two parallel straight lines, the corresponding angles are Equal.

2.When a transversal cuts two parallel straight lines, the alternate angles are equal.

3.When a transversal cuts two parallel straight lines, that pair of interior angles on

the same side of the transversal are supplementary,

4.When a transversal cuts two lines, such that the pairs of corresponding angles are equal, then the lines have to be parallel.

5.When a transversal cuts two lines, such that the pairs of alternate interior angles are equal, the lines have to be parallel.

6.When a transversal cuts two lines, such that the pairs of interior angles on the same side of the transversal are supplementary, the lines have to be parallel

**Here AB||CD and EF transversal. 3 and 6 , 4 and 5 are alternate angles to each other.**

**1 and 5, 3 and 7, 2 and 6, 4 and 8 are corresponding angles to each other.**

** **

**Definition**** : **If the corresponding angles made by a transversal are equal, the two straight lines are parallel.

In the figure ∠*PQR *= 55^{0} ,∠*LRN *= 90^{0} and *PQ *ll *MR*. Which one of the following is the value of ∠ *MRN *?

- 35
^{0}b. 45^{0}c. 55^{0}d. 90^{0}