Two column proof showing segments are perpendicular | Congruence | Geometry | Khan Academy

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Using triangle congruency postulates to show that two intersecting segments are perpendicular
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Geometry on Khan Academy: We are surrounded by space. And that space contains lots of things. And these things have shapes. In geometry we are concerned with the nature of these shapes, how we define them, and what they teach us about the world at large--from math to architecture to biology to astronomy (and everything in between). Learning geometry is about more than just taking your medicine ("It's good for you!"), it's at the core of everything that exists--including you. Having said all that, some of the specific topics we'll cover include angles, intersecting lines, right triangles, perimeter, area, volume, circles, triangles, quadrilaterals, analytic geometry, and geometric constructions. Wow. That's a lot. To summarize: it's difficult to imagine any area of math that is more widely used than geometry.
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[@ladybloodstone3952]

anybody else here to try to learn this before a test but still doesn't get it... because that's why I'm here 😭

[@kawaiibunnbunn]

me. 😭😭 i have a quiz tmrw but i don’t get anything-

[@gnomey5421]

Yeah

[@1auren]

same

[@soook569]

yeah khan academy has saved my life today

[@H.qx00]

ME I SWEAR TMR I HAVE A GEO TEST

[@Will-eg1uu]

I can’t wait to prove why a triangle is congruent in 10 years! Thanks public school geometry😊

[@MagicCookie2747]

factuallll

[@halei6h]

don’t worry it’s private school too!😊😊💔

[@qazwsxedcrfvtgb8877]

It's all about using your brain

[@kaaynn-rn]

I’m strong in algebra but a dying child in geometry. Thank you so much, I feel so behind in geo class and the one struggling the most.

[@Iliketurtles597]

Same I feel u😭

[@thrumwolf9583]

I’m a dead goat in both

[@Charlie-qe6lv]

As a math teacher, it seems that students are EITHER good in Geometry OR Algebra.

[@l2c145]

you are definitely not alone, i always feel like im the odd one out in the class...

[@l2c145]

@@thrumwolf9583 same here

[@abbybennett6307]

You can't just say "obvious" you have to use theorems and such for your reasons. Such as reflexive, CPCTC can be used a lot in the problem but is not. Could have saved a heck of a lot of steps by using CPCTC.

[@alexgeorge1090]

Abby Bennett what does cpctc stand for

[@aidanrobleto9013]

Corresponding Parts of Congruent Triangles are Congruent

[@Latency345]

Well he’s not exactly a teacher.

[@dinnerboons1504]

@@Latency345 well he’s a guy hired to teach people.

[@strunkshade]

I think it’s reflexive prop of congruence

[@nyx405]

The reason of CE = CE can be "reflexive property"

[@wilburforce8046]

because its combat evolved ;D (halo=best math teacher)

[@Latency345]

mathsonboarMeasures are the same because it’s the same unit

[@AK-gp7jb]

Wouldn't CA=CA because of the reflexive property of inequality

[@theresazheng1019]

@@AK-gp7jb it's equality

[@szymongwozdz2338]

I was literally about to say that

[@noufbts1137]

you make it look easy 😭

[@Latency345]

True enough

[@chrissybuddy9083]

03:02 - the property is also called Reflexive ( a quantity is Congruent or equal to itself)

[@janedoe-yf4dm]

if i had used the reason he used i would have gotten points off. no math teacher would have ever accepted a reason as "obvious from diagram"; and my geometry math teachers were nice! lol.

[@hannam78]

Instead of obvious it should've been reflexive property of equality

[@QueenKaiii]

that’s what i was thinking too😂

[@hannam78]

I hate geometry. I hate proofs. That's straight up...but this has helped so munc

[@lexilovesu2906]

Do you like geometry yet? Its been 6 years hehe

[@m1qu3l87]

still hates geometry and never used it in their job probably

[@z4blu3m1n]

Same i hate geometry, I have no problem with the other questions except with statements and reasons 😂 its like they don't make senseee

[@morganfranks92]

Remember guys, there's no ASS in math.

[@spaceplex5079]

Morgan Franks what...aw man, no ass for me

[@josephan5159]

I was gonna ask that just now I said it at school teacher thought it was a joke :/

[@spaceplex5079]

J-Hope II Hobi that's the joke tho

[@szymongwozdz2338]

Classic

[@dnghn.design]

Im dying lmaoooo

[@josephan5159]

You can't say obvious when you are giving a reason....

[@klimis9708]

The most confusing part of math. Me: gets perfect score in my math solutions. Also me: gets zero in two collumn proof. Like seriously this part of math is just confusing and killing my brain cells

[@maddie_ha]

Well, on the tests the shapes are not that simple

[@bofaasa]

thanks for helping prove a line is going through a triangle!

[@crzyderpkity7548]

I'm just trying to learn how to do my homeschool geometry ;-;

[@rhoadess]

I can do this geometry well, and it's fun to me. If only I could apply such reasoning when I do other real life things, from fixing the lawn mower, to making toast, down to thinking about my own thinking. I think i'll start trying to do that.

[@robertlitchmore6211]

🤓

[@alexdoesart43]

How is it going? It's been 11 years

[@allopjay.3061]

Bro how I’m dying trying to do this 😢

[@Systolic_Gaming]

8:27 supplementary thank you very much

[@immajorlygaygayiam2899]

Isnt helpful beause in my Geometry class Two Column Proofs are way differnt on the "Reasons" side. All these postulates are things i've never heard of.

[@chriscao5307]

+The Incredible True Story this is helpful because your school is way behind and postulates is known everywhere

[@macy4734]

Same. We call them "angle addition postulate" or "segment addition postulate"

[@huntergreer1303]

Thanks for doing what my teacher couldn’t actually teaching me proofs

[@thedemolisher4887]

I got so confused from step 9 when you stated that the triangles are supplementary without first proving whether if they form a linear pair or not. You seemed to have assumed from the diagram that Angle E formed a straight angle though logically it's true but it would have been better understood if you actually reviewed to us why. I mean afterall, what may be obvious to you may not be obvious to some other people so it would be a favor on their side.😊

[@SB-fo7em]

THE DEMOLISHER exactly

[@ascai3393]

actually, in my geometry book at least it said that certain things are safe to assume such as the straightness of a line in a diagram. so if it looks straight, it is in the problem. it was in our first chapter

[@ascai3393]

also, there is a better reason if you don't believe that one.the original question asked to prove the two lines perpendicular, meaning they have to be straight anyways.

[@alexdoesart43]

Considering it is given that DB is s consecutive line, it is implied that E is a straight angle. You could state that, but it isn't necessary

[@trevohngreen3788]

Dude I have been stuggling with this for the longest thank you SOOOOOOO MUCH 🙏🏾🙏🏾🙏🏾🙏🏾

[@virus4d903]

Geometry, very ez, but when we have to do statement, and reason, its the end of the world

[@its_me_shane]

anyone who still checks the comments, go to 2:43 and then after a couple seconds go back to 2:43 and repeat

[@unknownsponge14]

before step 9...state that they are a linear pair by the linear pair definition, then you can state that they are supplementary

[@Richard-y7x2i]

Proofs is something I really had trouble in, this video helped a lot. Thanks Sal :-)

[@erlen428]

Why wont math youtubers make crash courses. Crash courses makes explaining better, it keeps students from legit sleeping.

[@allisonpamer7396]

i have my math final tomorrow. thank you

[@noammanakermorag9538]

Woah it took me way more lines in my attempt

[@graceclemen9581]

Love math. Math is fun and shit like that. I shouldn’t have to explain that I’m right. People just need to be more friggin trusting!!! Let me be right!!

[@TheBest-lw2de]

What the fuck I didn't understand a thing

[@bruh-rk8yh]

The Best7878 same

[@ZestyPro7]

very helpful!

[@Prosperroify]

It seems like somewhere in there we had to prove the 90* angles by dividing 180*/ 2. Not just say "they are 90* because they are supplementary", because that is not ALWAYS true. See towards end.

[@88roro11]

holy shit i sucked at proof.. but if this was around when i was studying it for, "school" i would have done much better

[@indianash1]

couldn't you say that CA is congruent to CA because of the reflexive property?

[@ijaabogarad5412]

you are not even using real proofs, you are using obvious instead of reflexive

[@wilburforce8046]

yea.......obvious is not going to fly for an answer during my final xD

[@luisishere987]

Ijaabo Garad Right? Is this guy even taking this seriously?

[@bruhmomentum1387]

​@@luisishere987 bruh chillllll you don't have to watch it if you don't like it.... That's good that you know the actual names of the theorems,,,note that this video was made in like 2011 soooooooo maybe standards were different from now.

[@Paragon._.]

It took 2 weeks for the teachers to try to get me to understand but it took me only 10 minutes after watching this video

[@whengale]

I don't understand how it's proven or implied that line segment DB is a straight line, which seems to be something that statements 9 and onwards depend on. It seems to me that angle DEB could be 182° or 179° or 177°, etc., for all we know. 🤷‍♀️

[@unknownsponge14]

congruency is CPCTS

[@russmaserati2714]

Dimitri Baldauf CPCTC*

[@amyreynoso]

Corresponding parts of congruent triangles are congruent

[@aidenking44]

and what if your not able to use other statements in reasons. like we have to use theorems and postulates to give reasons to statements.

[@unknownsponge14]

The odvious is the reflexive property of equality...never put obvious down

[@dnghn.design]

I think its Transitive

[@dnghn.design]

Nvm

[@BigFreakingCacodemon]

Super helpful! What program are you using?

[@clemontnyethescienceguy6623]

smoothdraw 3

[@HandsomeDevil456]

I proved this in the exact same way. Nice!

[@MichaelHollomon]

How did we prove that DEB is a straight angle? Just from the assumption that DB is a line?

[@physicssimplified1769]

I have a question what could be the solution of this question: find the perimeter of a quadrilateral ABCD with ab =8cm bc=6cm and ad=ac

[@elizabethziants7811]

This helped. Thank you!

[@JiovanniCintron]

I understand it but I don’t remember all the postulates properties and other stuff

[@aidenking44]

yeah thats what i was thinking : "reflexive p of c"

[@user-ih1ex3rr6m]

Isn't the third one reflexive property of congruent angles?

[@MrBosscrown]

Thanks this helps so much

[@anniegao9105]

I'm always struggled in some math problems.

[@user-jw5db2wv3g]

Can someone pls answer this, LESSON 4.5 PROVING RIGHT TRIANGKES CONGRUENT TWO COLUMN PROOF. Plsssss

[@Leeluke22]

Instead of obvious isn't suppose to be reflexive?

[@i_want_potato]

I'm here because my teacher has not been here for the first 3 days of this unit and I have a test a few days later

[@summersun4235]

Thanks so much!!!

[@k4y685]

My mans put obvious as a reason...

[@sleepyva1814]

He was just simply bigger brained then his peers

[@alyssa.incog.8187]

reflexive??

[@zahinhuq7028]

I think that There is a reflexive of reflective Postulate. Instead of writing Obvious, u can put them. o_O

[@brd8764]

The rules apply so it is a fixed maths there is nothing measured but explained imagined worked out describd.

[@piotrpodsiadly2519]

but how do you know E is a point that is the closest to B and D on the line CA

[@ranaalanany2624]

why don't we prove the congruence of DEC and BEC so the angels will be congruent?

[@malissalovesmusic]

CA=CA because of reflexive

[@marksoriano7873]

Eyyy im pulling out my hair here, why did you not state reflexive property?

[@calliasroom]

This was great

[@Anthaneus]

Khanacademy

[@Swagg0523]

excatly what i need had proof

[@dillonspellman4912]

thank you sal you saved me again

[@siddakid671]

+Dillon Spellman same

[@chriscao5307]

@the Incredible True Story this is helpful because u dont teach right and postulates is known everywhere

[@Hippoman141]

@indianash1 yes you can

[@OliT0210]

Yes.

[@iamzeturtel]

Totally me not trying how to learn to do this last minute

[@chopperdeath]

Wasn’t there a symbol or word you write at the very bottom of your proof basically saying “It is proved”? Like a Latin phrase or something? Or am I fooling myself?

[@SB-fo7em]

Broooooooooooooo step nine got me confused af how’d you know that line de and line eb is a linear pair

[@LOGINxORxREGISTER]

dat voice

[@OliT0210]

Isn't there also RHS? (right angle, side, hypotenuse)

[@CottageCheese77]

HL, hypotenuse leg

[@khushboobhatt5710]

85:40::77 plz ye koi solve kar k dedo

[@sgstud88]

no

[@TheXdmsify]

Your Awesome ^_^

[@albertmendoza1468]

Im sorry but this is the first video that I was disappointed. You can't say 'obvious' in proving something, you need to provide us reason :(

[@jesussaquin6266]

Most useless type of math

[@Meep_SE.R.5]

Álex Lopez agree brother

[@Meep_SE.R.5]

Bernhard Riemann you got a point but i dislike this unit because its so much to remember also i dont see this being helpful for my future career

[@BVinnyC]

Bernhard Riemann He meant geometric proofs. Other ways of proving take much less time and actually prove your equation

[@jesussaquin6266]

@@BVinnyC yea if proving if two lines are perpendicular why not take a protractor and measure them. Math specially for engineers should be applied mathematics not other. Therefore this is no better than studying abstract art