Question

5. Examine whether Ab and CD are parallel in each of the following cases

angle b=70 degree, angle Z=70degree​

Answer 1

Answer:

A line segment has two end points.A ray has only one end point (its vertex).A line has no end points on either side. This chapter throws light on topics such as related angles, pair of lines. The chapter deals with different types of angles and lines. The types of angles discussed in this chapter are as follows:Pairs of Angles         ConditionTwo complementary anglesMeasures add up to 90°Two supplementary anglesMeasures add up to 180°Two adjacent anglesHave a common vertex and a common arm but no common interiorLinear pairAdjacent and supplementaryA linear pair is a pair of adjacent angles whose non-common sides are opposite rays.

All the types are discussed in detail and are supplemented with examples and short questions. 

Under the topic pair of lines, various sub-sections are discussed namely:Intersecting linesTransversal Angles made by a transversalWhen two lines intersect (looking like the letter X) we have two pairs of opposite angles. They are called vertically opposite angles. They are equal in measure.A transversal is a line that intersects two or more lines at distinct points.Six angles discussed in this section:

1. Interior angles

2. Exterior angles

3. Pairs of Corresponding angles

4. Pairs of Alternate interior angles

5. Pairs of Alternate exterior angles

6. Pairs of interior angles on the same side of the transversalTransversal of parallel linesSubsequently the topic- Checking for Parallel Lines is also discussed in the chapter- Lines and Angles. When a transversal cuts two lines, such that pairs of corresponding angles are equal, then the lines have to be parallel. When a transversal cuts two lines, such that pairs of alternate interior angles are equal, the lines have to be parallel.When a transversal cuts two lines, such that pairs of interior angles on the same side of the transversal are supplementary, the lines have to be parallel.Several diagrams are also present in the chapter wherever required. 

The chapter consists of a set of questions to test the basic understanding of the chapter followed by the summary of the discussion for quick recall.