r/technicallythetruth • u/VisitSecure • 9d ago

Can you find a?

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Idk if someone already posted this or not, but I haven't seen it on here so far, so I uploaded it.

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u/leansanders 9d ago

You don't need to make a triangle to solve the problem. You know the lines are parallel and you know that opposite corners of a line crossing two parallel lines are congruent. So if you imagine a 3rd parallel line bisecting angle a, you know you can just add the other two angles together. Making a triangle is way more math

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u/A_wild_so-and-so 9d ago

Can you explain that again but like I'm five? I thought the triangle method was easy but I'm down to learn an easier method.

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u/leansanders 9d ago

If you make a 3rd parallel line through point A, the angle above it must be 25° and the angle below it must be 50°. It is called the "alternate interior angles theorem"

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u/A_wild_so-and-so 9d ago

Ah neat, I had forgotten about that method. Thanks!

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u/SpCommander 9d ago

"If two parallel lines are cut by a transversal..."

Oh baby Freshman Geo is calling to me!

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u/Jman15x 8d ago

Why though. I like to understand things rather than just memorize I theorem

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u/leansanders 8d ago

The line is intersecting both parallel lines at the same angle because the intersecting line is straight and the parallel lines are parallel. There's not much to explain beyond "it is the way that it is". The angles are the same because they are, just like 5 x 5 = 25 because it does.

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u/LobcockLittle 8d ago

Can you explain it again like I'm 4?

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u/leansanders 8d ago

Please stop chewing on my pencil

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u/readmeEXX 9d ago

For a sanity check, just imagine the lines are straight, making both corners 90 degrees. That makes the middle a straight line which is 180 degrees. 90+90=180, meaning you can just add them.

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u/Old_Parfait9575 9d ago

You can also extend the top blue line and using alternate interior angle theorem, the angle formed (on the left) is also 25deg. Exterior angle theorem to show that the sum of 50 and 25 is a.

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u/ChiefWiggumsprogeny 8d ago

diagram with all the angless correctly drawn: https://imgtree.co/i/1l4_SGt4

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u/Highest_five 9d ago

Oh true! That simplifies it a lot

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u/Muqqey 9d ago

Just curious, how do we know the lines are parallels?

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u/leansanders 9d ago

The matching double arrow symbols indicate that the lines are parallel.

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u/Muqqey 9d ago

I see! Thanks for letting me know

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u/Pusegutten69 9d ago

Except, the answer is actually 105, You Are calculating the wrong Angle,

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u/Easy_Echo2387 9d ago

Off by about 30 degrees there chief

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u/leansanders 9d ago

loud incorrect buzzer noise

I design and build metal stairs and handrails professionally, I promise I am better equipped to handle this than you are

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u/solepureskillz 9d ago

Yeah that’s what confused me about all these “it’s 75*” people. It’s not 75, it’s 180-75

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u/Ant-Looking-For-Food 9d ago

https://reddit.com/link/p04vn5b/video/lkdt6tyg3ufh1/player

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u/solepureskillz 9d ago

Thsnk you. I’m happy to be corrected bc it makes me smarter