"Properties of Parallel Lines" PPT download

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"Properties of Parallel Lines" PPT download

Part One: Review and Review

What are the methods to determine parallel lines?

How to identify parallel lines

⑴The parallel angles are equal and the two straight lines are parallel

⑵The internal angles are equal and the two straight lines are parallel

⑶ Interior angles on the same side are complementary and two straight lines are parallel

Properties of Parallel Lines PPT, Part 2: Properties of Parallel Lines

Properties of parallel lines (1)

Two parallel lines intersected by a third straight line have equal angles.

In short, two straight lines are parallel and have equal angles.

∵ AB ∥ CD (known)

∴ ∠1=∠2

(Two straight lines are parallel and have equal angles)

As shown in Figure 7-5-2, AB∥CD, straight line AB, CD is intercepted by straight line EF. ∠1 and ∠2 are internal offset angles. The process of saying ∠1=∠2 is as follows:

Reason: ∵ AB∥CD (known)

∴ ∠1=∠3 (the two straight lines are parallel and have equal angles)

∵ ∠2=∠3 (the two vertex angles are equal)

∴∠1=∠2 (equivalent substitution)

Conclusion: Two straight lines are parallel and their internal offset angles are equal.

Properties of parallel lines:

1. Two straight lines are parallel and have equal angles.

2. Two straight lines are parallel and their internal offset angles are equal.

3. Two straight lines are parallel and the interior angles on the same side are complementary.

PPT on the nature of parallel lines, part 3: Consolidation exercises:

1. If AD//BC, according to _______________, we can get ∠B=∠1

2. If AB//CD, according to _______________, we can get ∠D = ∠1

3. If AD//BC, according to _______________, we can get ∠C＋_____=180°

Example 1: As shown in the figure, AD∥BC, AB∥DC, ∠1=100°, find the degrees of ∠2 and ∠3

Solution: Because AD∥BC

So ∠1=∠2 (the two straight lines are parallel and the internal offset angles are equal)

Because ∠1=100° (known)

So ∠2=100° (equivalent substitution)

Because AB∥CD (known)

So ∠1+∠3=180° (two straight lines are parallel, and interior angles on the same side are complementary)

Because ∠1=100° (known)

So ∠3=180°-100°=80°

(equivalent substitution)

PPT on the nature of parallel lines, part 4: Practice 1 Practice

1. As shown in the figure, AB // DC, AD // BC, and ∠1= 60°, find the degrees of ∠2, ∠3, ∠4.

2. As shown in the figure, AD // BC, ∠B= 58 °, ∠D=136 °, find the degrees of ∠A, ∠C

3. The picture shown is a trapezoidal incomplete jade piece excavated in the world-famous Sanxingdui archeology. The staff has measured ∠A=115° and ∠D=100° from the jade piece. Given the two bases AD//BC of the trapezoid, please find the measures of the other two angles.

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"Properties of Parallel Lines" PPT:

"Properties of Parallel Lines" PPT Part One Content: Knowledge Review 1. If B=1, according to _______________, we can get AD//BC 2. If 1=D, according to _______________, we can get AB//CD 3. If B+BCD=180, according to___..

"Properties of Parallel Lines" PPT courseware download:

"Properties of Parallel Lines" PPT courseware download Part 1 content: Do a hands-on experiment: Select any two parallel lines a, b on the prepared grid book (1) Draw a straight line c and parallel lines a, b arbitrarily intersect. (2) Choose any pair of co-positioned angles and measure them with a protractor...

"Property Theorem and Determination Theorem of Parallel Lines" PPT courseware 3:

"The Property Theorem and Determination Theorem of Parallel Lines" PPT Courseware 3 Knowledge Review: (1) What is a proposition? How many categories can propositions be divided into? (2) What parts does a proposition consist of? (3) What is the general narrative form of a proposition? Let's talk about it. If two angles are right angles...

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Update Time: 2024-09-06

This template belongs to Mathematics courseware Hebei Education Edition Seventh Grade Mathematics Volume 2 industry PPT template

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