Name: Determining congruent triangles example
Uploaded: 2020-04-29T18:25:11.000Z
Duration: 4 min 31 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

- [Instructor] We have four triangles depicted here,

Basic passive voice

And we are asked which two triangles must be congruent?

So pause this video, and see if you can work this out

on your own before we work through this together.

All right, now let's work through this together.

This triangle IJH, they've only given us two angles.

I can figure out the third angle because the sum

of the angles of a triangle have to add up to 180 degrees.

in order to judge which of these triangles are congruent.

So first of all, what is going to be the measure

Pause the video, and try to think about that.

I'm just giving their measures in degrees here.

And then if I subtract 118 from both sides,

I guess is another way of thinking about it.

I could put everything in terms of degrees if you like.

Well, this one has an 82-degree angle and a 62-degree angle,

So we know that the third angle needs to be 36 degrees,

if you need to get to 180, it has to be 36.

We just figured that out from this first triangle over here.

Now, if we look over here, 36 degrees and 59,

this definitely looks like it has different angles,

but let's figure out what this angle would have to be.

And I'm just thinking in terms of degrees here.

this is going to be equal to, what is this?

And then if I subtract 95 from both sides,

And so this is going to be equal to 85 degrees.

And then this last triangle right over here,

I have an angle that has a measure of 36,

So let's ask ourselves, now that we've figured out

to look at these bottom two triangles and say,

hey, look all of their angles are the same.

You have angle, angle, angle and angle, angle, angle.

If you have three angles that are the same,

But we don't have any length information for triangle IJH.

You need to know at least one of the lengths

of one of the sides in order to even think,

And so we can't make any conclusion that IJH and LMK,

triangles IJH and triangles LMK are congruent to each other.

Now let's look at these candidates up here.

We know that their angles are all the same,

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Determining congruent triangles example

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