Bearclaws72:

Elba writes the following proof for the theorem: If the diagonals of a quadrilateral bisect each other, the quadrilateral is a parallelogram: Elba's proof 1. For triangles AOB and COD, angle 1 is equal to angle 2 as they are vertical angles. 2. AO = OC and BO = OD because it is given that diagonals bisect each other. 3. Therefore, the triangles AOB and COD are congruent by SAS postulate. 4. Similarly, triangles AOD and COB are congruent. 5. By CPCTC, angle ABD is equal to angle CDB and angle ADB is equal to angle CBD. 6. As the _______________ are congruent, the opposite sides of quadrilateral ABCD are parallel. 7. Therefore, ABCD is a parallelogram. Which is the missing phrase in Elba's proof?

10 months ago
Bearclaws72:

1 attachment
10 months ago
Bearclaws72:

Which is the missing phrase in Elba's proof? alternate interior angles corresponding angles corresponding sides opposite sides

10 months ago
Bearclaws72:

@Angle

10 months ago
Bearclaws72:

Im doing every other question so you should only be doing five @Angle Senpai XD

10 months ago
Angle:

I don't mind checking all of them as long as you put in some effort to learn as we go

10 months ago
Bearclaws72:

Uhhhhhh sure Dammit Im gonna choke XD Ill try and put an effort

10 months ago
Bearclaws72:

On this one I actually wanted to say Reflexive property >.>

10 months ago
Angle:

in step 5 "angle ADB is equal to angle CBD" what are these angles called? RwmSf-B8SL2NjgVnx5O4zQ.png

10 months ago
Bearclaws72:

Is it Transversals?

10 months ago
Bearclaws72:

Wait no

10 months ago
Bearclaws72:

I hate vocab

10 months ago
Angle:

yeah, it has to do with transversals

10 months ago
Bearclaws72:

So it is transversals?

10 months ago
Angle:

I'm asking what those angles (I drew) are called http://www.mathsisfun.com/geometry/parallel-lines.html

10 months ago
Bearclaws72:

Line segments -_-

10 months ago
Angle:

What are these ANGLES called ltYbXoWtQ8SKGWqop-hByw.png

10 months ago
Bearclaws72:

Alternate interior

10 months ago
Angle:

AWESOME now what are these ANGLES called? RwmSf-B8SL2NjgVnx5O4zQ.png

10 months ago
Bearclaws72:

Dammit. Alternate interior again?

10 months ago
Angle:

yup so there's your answer "angle ADB is equal to angle CBD" means that angles ADB and angle CBD are alternate interior angles. Once you are able to say "that line is a transversal" => you can say "those two lines are parallel"

10 months ago
Bearclaws72:

Hell yah alright next question XD

10 months ago
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