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Mathematics 18 Online
Sarah10:

proof and reasoning

Sarah10:

http://prntscr.com/hk5a6c

Sarah10:

@563blackghost

Sarah10:

anyone..

Sarah10:

@Vocaloid

563blackghost:

heyo, let me take a look at it...

Sarah10:

thnxx

563blackghost:

this might take a while...i have done triangles but this seems a bit different from the ones i've done...

Sarah10:

take your time

Sarah10:

i think it needs like one of those ssa aas yknow rules

Angle:

SSA is not a proper rule you can use btw

Angle:

in any case AB = AC by definition of isosceles triangle

Angle:

XB = XC by definition of midpoint

Angle:

then we want to say that <ABC = <ACB (I forget the reason) in order to use SAS to say the triangles BAX and CAX are similar triangles then CPCTC to say that <BAX = <CAX

563blackghost:

hmmm We are given that \(\bf{\triangle ABC}\) is Isoceles with Vertex \(\bf{\angle BAC}\) and that \(\bf{X}\) is the midpoint of \(\bf{BC}\). Since we are told that the triangle is isoceles because of the vertex it would mean that \(\bf{AB=AC}\) due to def. of isosceles triangle. Since X is the midpoint of \(\bf{BC}\) this means that the segment is split in the middle, this saying that \(\bf{BX=BC}\).. ....and @Angle already said this....

563blackghost:

well then... I would agree with the CPCTC...

Angle:

@563blackghost I like the way you explained it better :) I missed reason for one of the things, do you know what it is? I can't think of it

563blackghost:

Reflexive probably? for AX=AX?

563blackghost:

no...wait that would be after...

Angle:

<ABC = <ACB it's the base angles of the isosceles triangle are equal I'm not sure what the specific rule is called or if you're allowed to use a rule like that in the proof

Sarah10:

Thank you both sooooooooooooo much!!

Angle:

|dw:1512618531620:dw|

563blackghost:

I wouldn't know how to apply that as part of the proof...i feel like im missing something...

Logic007:

Given X is the midpoint of BC Given |dw:1512618786105:dw|

Angle:

@Logic007 As I mentioned in my first comment, SSA cannot be used to prove triangle congruence

563blackghost:

Which means that BXA is right and CXA is right too. Meaning AX=AX thus having that angle BAX is congruent to CAX by CPTCTC...no??

Angle:

@563blackghost CPCTC doesn't work for SSA or SSS

563blackghost:

We proved that BX=CA, and we can see that BXA is right and CXA is right too meaning that BXA=CXA. They share a segment being AX=AX by reflexive. We proved triangle BXA= triangle CXA by SAS...corresponding sides are equal to each other so angle BAX = angle CAX... hmmmmmm

563blackghost:

no...i cant just assume right angle... darn

Angle:

ohhh yes that is another way to prove it but saying the perpendicular bisector of BC goes through X and A is a little difficult to prove; although it should have a name to this rule

563blackghost:

well for X to intersect vertex A would be definition of a bisector....

563blackghost:

Im thinking of saying BA=CA and BX=CX thus \({\angle XBA=\angle XCA}\) but i dont think that works....

563blackghost:

Are you sure this is the whole picture, cause the pic looks a little cut off (it could be showing right angles....) just asking @Sarah10

Sarah10:

yes

563blackghost:

ok

Sarah10:

i swear i have been trying to keep up .. can someone please summarize it if you have time

Angle:

|dw:1512620187832:dw|

563blackghost:

\(\color{#0cbb34}{\text{Originally Posted by}}\) @Angle @563blackghost CPCTC doesn't work for SSA or SSS \(\color{#0cbb34}{\text{End of Quote}}\) This does work. Did some researching.

563blackghost:

What reason did you find for \(\bf{\angle ABX = \angle ACX}\)? Just wondering.

563blackghost:

XD i didn't see that...ah ok

Angle:

http://www.mathwarehouse.com/geometry/congruent_triangles/isosceles-triangle-theorems-proofs.php Base Angles Theorem for Isosceles Triangles

563blackghost:

writing this one down....

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