Lesson 86. Properties of Parallel Lines

T6-criterion for parallel lines

[bgcolor=orange] If two lines are intersected by a third line, and alternate interior (or exterior) angles are equal, then the original two lines are parallel. [/bgcolor]

New Resources

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探究長方形對角線上的正方形數目
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רישום חופשי
Flip A Bunch of Coins

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Trigonometric Ratios
All triangles are equilateral
Figure 6.8 Enter an Equation (800x500)
Solar System
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Curve Sketching
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