Gina wrote the following paragraph to prove that the segment joining the midpoints of two sides of a triangle is parallel to the third side.

Question

anonymous · Answer

attachment

anonymous · Answer

thats the file problem, help??

anonymous · Answer

@ash2326 help?

anonymous · Answer

so any ideas?

ash2326 · Answer

Yeah, let's work upon it
Let's draw the triangle first

ash2326 · Answer

|dw:1349018270880:dw|
Do you understand the figure?

anonymous · Answer

Yes

anonymous · Answer

But how do you know where x1 and y1 are??

ash2326 · Answer

No, it's just a figure. It's just for understanding 
We don't have to know the coordinates for this

anonymous · Answer

Oook then, moving on

ash2326 · Answer

OK, Let's mark the midpoints|dw:1349018594150:dw|

anonymous · Answer

Ok

ash2326 · Answer

@kdzsnake do you understand the steps Gina do, she finds slope of DE and AC?

anonymous · Answer

yea i think so

ash2326 · Answer

So, there is a minor mistake or we could say that she misses to mention a statement

ash2326 · Answer

@kdzsnake what do you think it is?

anonymous · Answer

Where??? It looks ok?

ash2326 · Answer

"Parallel postulate"
That's unheard
read the options carefully, would you?

anonymous · Answer

Ohh i see, Ok so where is is finding the slope of DE she uses the wrong equation?

anonymous · Answer

The slope of segments DE and AC is not 0..?

ash2326 · Answer

Do you think it's not 0?
then check her calculations again

anonymous · Answer

nevermind haha...

anonymous · Answer

Segments DE and AC are parallel by definition of parallel lines..... haha

ash2326 · Answer

Nope, I really mean it. Check to make sure you understand it

anonymous · Answer

YEs I do understand the formula she uses,

ash2326 · Answer

So, you understood and sure which option is correct?

anonymous · Answer

YEs she does the equation correct, so through process of elimination it can be D, and it can't be A because that is true, its not correcting anything and then I don't know what"The coordinates of D and E were found using the Distance between Two Points Postulate" means and B makes sense?

ash2326 · Answer

You are right, it's b
since parallel lines have same slope

ash2326 · Answer

"The coordinates of D and E were found using the Distance between Two Points Postulate"
We used midpoint formula, so this option gets automatically dropped

anonymous · Answer

Thanks! for your help, I have one more question maybe you could help with?

anonymous · Answer

attachment