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आर्यभट्ट
आर्यभट्ट
15:02
Hi sir actually I had a question what would be the geometrical condition necessary for three lines to form an triangle I tried searching on internet no particular proof was available
@robjohn
Plus is there a general proof on sum of triangle cannot exceed 180
 
2 hours later…
robjohn
robjohn
17:12
Three lines always form a triangle unless they intersect at a single point (coincident). In that case, the triangle is degenerate (a single point).
robjohn
robjohn
17:25
Do you know about alternate angles?
आर्यभट्ट
आर्यभट्ट
hi
@robjohn
yes
can u help me in getting proof 180 degree one
robjohn
robjohn
Okay so draw a triangle and then a line through a vertex, parallel to the side not containing that vertex. Then look at the alternate angles.
Then note that a straight angle is 180°
आर्यभट्ट
आर्यभट्ट
yes
robjohn
robjohn
That shows that the sum of the interior angles is 180°
आर्यभट्ट
आर्यभट्ट
okay sir can u help in getting understand congurence of traingles
basically, what congruence describes is the properties?like angles side length etc
@robjohn
robjohn
robjohn
17:38
I am not sure what you mean.
This sounds like a question best answered by reading a section on triangle congruences. There is a lot there.
If you have questions on a particular result, I can help there, but going through all that you seem to be asking about is a lot.
Here is a Khan Academy page on this.
robjohn
robjohn
18:16
user image
Proof that the sum of the three angles in a triangle sum to 180°
using alternate angles.

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