"Parallel Lines" Intersecting Lines and Parallel Lines PPT Courseware 2

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"Parallel Lines" Intersecting Lines and Parallel Lines PPT Courseware 2

1. Definition of parallel lines

Two straight lines that do not intersect in the same plane are called parallel lines.

think about it

(1) If there is no "in the same plane", are two straight lines that do not intersect parallel?

(2) Can the "straight line" in the definition be changed to "line segment or ray"?

The parallelism of line segments or rays refers to the parallelism of the straight lines on which they lie.

Observe the cuboid as shown in the figure and fill in the blanks:

(1) Use symbols to indicate the positional relationship between the following two edges:

A1B1 AB, AA1 AB,

A1D1 C1D1, AD BC.

(2) The straight lines where A1B1 and BC lie are two non-intersecting straight lines, and they are _____ parallel.

(fill in "yes" or "no"),

It can be seen that only two straight lines that do not intersect within ______ can be called parallel lines.

Use a ruler and set square to draw parallel lines

1. Drop: Drop one side of the triangle ruler on a straight line

2. Lean: Place a straight ruler next to the other side of the triangle ruler

3. Push: Push the set square along the edge of the ruler until the first side of the set square just passes point P.

4. Draw: Draw a straight line along this side of the triangle ruler

What did you discover from the above practice? Tell me

Through a point outside the straight line, there is one and only one straight line parallel to this straight line. (Parallel Axiom)

Explanation: The conclusions people draw from long-term practice are called basic facts, also called axioms, which can be used as the basis for future reasoning.

1. The correct number of the following statements is ( )

(1) Two straight lines are parallel if they do not intersect.

(2) In the same plane, two parallel straight lines have one and only one intersection point

(3) There is and is only one straight line through a point that is parallel to the known straight line.

(4) Two straight lines parallel to the same straight line are parallel to each other

(5) The only positional relationship between two straight lines is intersection and parallel

A, 0 B, 1 C, 2 D, 4

2. Which of the following reasoning is correct ( )

A. Because a // d, b // c, so c // d;

B. Because a // c, b // d, so c // d;

C. Because a // b, a // c, so b // c;

D. Because a // b, c // d, therefore a // c.

3. It is known that both straight lines L1 and L2 pass through point P, and L1//L3, L2//L3, then L1 and L2 must coincide. This is because passing through a point outside the straight line, there is and is only one straight line parallel to the known straight line.

4. Which of the following statements is correct ( )

A. There is only one parallel line to a straight line

B. There is and is only one straight line parallel to the known straight line passing through a point.

C. There are two straight lines parallel to a certain straight line passing through a point.

D. There is and is only one straight line parallel to the known straight line through a point outside the straight line.

What I learned from this class is...

1. What are parallel lines?

2. Representation of parallel lines

3. How to draw parallel lines

4. Axioms and corollaries of parallel lines

5. The positional relationship between two straight lines in the same plane

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For more information about the PPT courseware "Parallel Lines Intersecting Lines and Parallel Lines", please click the Parallel Lines ppt Intersection Lines and Parallel Lines ppt tab.

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Update Time: 2024-10-18

This template belongs to Mathematics courseware People's Education Press Seventh Grade Mathematics Volume 2 industry PPT template

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