What is the value of x?

Question

anonymous · Answer

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terenzreignz · Answer

External angle theorem XD

anonymous · Answer

|dw:1363959863782:dw|

Can you calculate y ?

anonymous · Answer

yup

terenzreignz · Answer

It looks like @SheldonEinstein is already doing it directly... :)
Do as instructed, calculate y :D

anonymous · Answer

We have two methods here :

i) First calculating "y" 

ii) Using external angle theorem.

anonymous · Answer

The line is straight so does tht mean the line equals 180 dgrees

anonymous · Answer

ii) one is much easier.

anonymous · Answer

Yes @Fradycat you are on right track

anonymous · Answer

so : $ y + 100 = 180$ 

y = ?

anonymous · Answer

So it's 80

terenzreignz · Answer

Brilliant :)|dw:1363960017863:dw|

anonymous · Answer

Yes great work.

terenzreignz · Answer

Now, solve for x :)

anonymous · Answer

how

anonymous · Answer

Now I have the triangle with two angles given : 80 and 70 . The third one is unknown currently ... we have it as x : 

as the sum of all the angles of a triangle is 180 degree

So : 80 + 70 + x = 180 degrees.

getting it? @Fradycat

anonymous · Answer

is it 30 degrees

terenzreignz · Answer

I don't know, is it? :D
LOL
You got it :)

anonymous · Answer

Yes! So you have calculated "x" as 30 degree which is your answer.

anonymous · Answer

Thanks i actually learned how to do this

anonymous · Answer

Similarly you can do it by ii) method.

terenzreignz · Answer

NOW, let's forget we did that, and state the External angle theorem...
Say we have this triangle...
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The External angle theorem states that any external angle is equal to the sum of the two remote angles...
OR simply put
P = Q + R

anonymous · Answer

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anonymous · Answer

oh Thts simple enough

anonymous · Answer

That you have already got earlier. So @Fradycat stick to the method you have understood first and then proceed.

anonymous · Answer

:) Glad to hear that you got the ii) method.

anonymous · Answer

The abbreviation CPCTC stands for "Corresponding parts of congruent triangles are _____________."

terenzreignz · Answer

Care to take a guess? :D
If two triangles are congruent, then, say, two corresponding sides must be...?

anonymous · Answer

Congruent?

terenzreignz · Answer

Yep :D

anonymous · Answer

OMG thank i didnt want to take the chance of getting tht wrong

terenzreignz · Answer

Actually, it's chocolate :D

anonymous · Answer

Awesome

anonymous · Answer

Assume ABC DEF. If DF = 12, EF = 7, and AB = 17, what is the length of DE?