Proof: Vertical angles are equal | Angles and intersecting lines | Geometry | Khan Academy

Proving that vertical angles are equal

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[ciellonae]

please know that youre so very very helpful and i dont want you to ever stop teaching please

[freverntyurs]

its interesting how something which might seem very abstract can be solved with simple but direct logic.

[werraas]

I hate to be so precise, but if we're going to be technical here, then it isn't really correct to say that an angle is equal to another angle. However, you CAN say that the MEASURE of an angle is equal to the MEASURE of another angle. Alternatively, you could say the two angles are CONGRUENT. These rules are important for writing proofs that are technically correct.

[Cube_Box]

Regular "vertical":
This refers to something that's upright or perpendicular to the ground, like a wall or a tree standing tall.

"Vertical" in vertical angles:
Here, it describes the relationship between the angles based on their shared vertex. Imagine the two intersecting lines forming a big "X." The vertex is the point where the two lines cross in the center of the "X." Vertical angles are the two angles that are directly opposite each other at this vertex.

Basically it's relative to the "vertex", it has nothing to do with the definition of everyday "vertical"

[divoojilly]

i had my math test today. wish i had seen this video b4!!!

[msoni]

At 3:48, Sal could have done the substitution property resulting in angle CBE equaling angle DBA.

[az-mext]

How do you know DBE is always a straight angle?

[advikathegr]

you cant just leave it like that...even if it is very well explained it is required to finish the answer and now leave it in a -180 form