Parallel and Intersecting Lines | IT

Question 6

Observe Fig. 5.5 and describe the way the line segments meet or cross each other in each case, with appropriate mathematical words (a point, an endpoint, the midpoint, meet, intersect) and the degree measure of each angle.

Question diagram 1
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Solution
Understand the Question

To describe how line segments interact in a given figure, we use specific geometric terms:

  • Parallel lines/segments: Line segments that never meet or intersect, maintaining an equal distance throughout.
  • Intersecting segments: Line segments that cross each other at a single common point (point of intersection).
  • Meeting at an endpoint: Line segments that share a common vertex to form an angle of a given degree measure.

(i) Describe the way line segments ST\text{ST} and UV\text{UV} interact.

Step 1 · Observe Segments ST and UV

Diagram 1

Segments ST\text{ST} and UV\text{UV} are parallel to each other. They do not meet or intersect.

Answer

(i) Segments ST\text{ST} and UV\text{UV} are parallel and do not meet or intersect.

(ii) Describe the way line segments AB\text{AB} and CD\text{CD} interact.

Step 1 · Observe Segments AB and CD

Diagram 2

Segments AB\text{AB} and CD\text{CD} cross each other at a single point X\text{X}, which is their point of intersection.

Answer

(ii) Segments AB\text{AB} and CD\text{CD} intersect at point X\text{X}.

(iii) Describe the way line segments PQ\text{PQ} and OR\text{OR} interact.

Step 1 · Observe Segments PQ and OR

Diagram 3

Segments PQ\text{PQ} and OR\text{OR} are parallel. They do not meet or intersect.

Answer

(iii) Segments PQ\text{PQ} and OR\text{OR} are parallel and do not meet or intersect.

(iv) Describe the way line segments FG\text{FG} and FH\text{FH} interact and state the angle measure.

Step 1 · Observe Angle Formed by FG and FH

Diagram 4

Segments FG\text{FG} and FH\text{FH} meet at a common endpoint F\text{F} (the vertex).

FGH=115.3\angle \text{FGH} = 115.3^\circ

Answer

(iv) Segments FG\text{FG} and FH\text{FH} meet at point F\text{F}, forming an angle of 115.3115.3^\circ.

(v) Describe the way line segments IL\text{IL} and MJ\text{MJ} interact.

Step 1 · Observe Segments IL and MJ

Diagram 5

Segments IL\text{IL} and MJ\text{MJ} cross each other at a single point Y\text{Y}, which is their point of intersection.

Answer

(v) Segments IL\text{IL} and MJ\text{MJ} intersect at point Y\text{Y}.

Common Mistakes
  • Meeting vs. Intersecting: Confusing segments that meet at an endpoint (sharing a vertex to form an angle) with segments that cross/intersect through one another at an internal point.
  • Parallel Lines: Assuming non-touching segments are always parallel without verifying that they maintain an equal distance and would never meet even if extended.

More questions in IT

Q1

Context: Let us observe what happens when two lines intersect.

Q. How many angles do they form?

Q2

Can two straight lines intersect at more than one point?

Q3

In Fig. 5.2, if a\angle a is 120120^\circ, can you figure out the measurements of b\angle b, c\angle c and d\angle d, without drawing and measuring them?

Q4

Context: When two lines intersect each other and form four angles, labelled aa, bb, cc and dd, then a\angle a and c\angle c are equal, and b\angle b and d\angle d are equal.

Q. Is this always true for any pair of intersecting lines?

Q5

Can you draw a pair of intersecting lines such that all four angles are equal? Can you figure out what will be the measure of each angle?

Q6

Observe Fig. 5.5 and describe the way the line segments meet or cross each other in each case, with appropriate mathematical words (a point, an endpoint, the midpoint, meet, intersect) and the degree measure of each angle.

Q7

Are line segments ST\text{ST} and UV\text{UV} likely to meet if they are extended?

Q8

Are line segments OP\text{OP} and QR\text{QR} likely to meet if they are extended?

Q9

Name some parallel lines you can spot in your classroom.

Q10

Which pairs of lines appear to be parallel in Fig. 5.6 below?

Q11

Is it possible for all the eight angles to have different measurements? Why, why not?

Q12

What about five different angles — 6, 5, 4, 3 and 2?

Q13

Suppose, we have a transversal intersecting two parallel lines. What can be said about the corresponding angles?

Q14

Context: Activity 5 In Fig. 5.20, draw a transversal tt to the lines ll and mm such that one pair of corresponding angles is equal. You can measure the angles with a protractor.

Q. Are you finding it hard to draw a transversal such that the corresponding angles are equal?

Q15

Draw two more parallel lines using the long side of the set square as shown in Fig. 5.22. How do you know these two lines are parallel? Can you check if the corresponding angles are equal?

Q17

Why are lines ll and mm parallel to each other?

Q18

Is there a relation between 3\angle 3 and 6\angle 6? You could try to find the relationship by taking different values for 3\angle 3 and see what 6\angle 6 is. Once you find a relation, try to justify it or prove that this relation holds always.

Q19

There do not seem to be any parallel lines here. Or, are there?

What causes these illusions?

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