# Parallel Lines

The lines that do not intersect each other are called Parallel lines.
Example: Railway tracks,lines on the note book etc.

Transversal : The line which cuts the two parallel-lines in two distinct points is called transversal.

The eight angles are formed by parallel-lines and transversal , they are Types of Angles made by Transversal with two Lines
1) Corresponding angles : There are 4 pairs of corresponding angles. These angles are formed on letter “F”.

If the lines are parallel then the measures of corresponding angles are equal.
 Corresponding Angles ∠a = ∠e ∠d = ∠h ∠b = ∠f ∠c = ∠g

2)Alternate interior angles : There are 2 pairs of alternate interior angles. These angles are formed on letter “z”.

If the lines are parallel then the measures of alternate interior angles are equal.

 Alternate Interior Angles ∠d = ∠f ∠c = ∠e

3)Interior angles on the same side of transversal : There are two pairs of interior angles. These angles are formed on letter “C”.

If the lines are parallel then the interior angles on the same side of transversal are supplementary.( sum up to 180)
 Interior Angles ∠a + ∠b = 1800 ∠c + ∠d = 1800

4) Alternate exterior angles : There are two pairs of alternate exterior angles. Alternate Exterior Angles ∠a = ∠g ∠b = ∠h

If the lines are parallel then the measures of alternate exterior angles are equal.
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Practice

Use the following figure and answer the given questions: 1) State all the corresponding angles.
2) Give the names of alternate interior angles.
3) If m∠b = 400 then find the remaining angles and state the reasons for it.
Basic Geometry

Point
Lines
Angles
Lines and Angles
Complementary angles
Supplementary angles
Vertically Opposite Angles
Linear Pair Angles