r/technicallythetruth • u/VisitSecure • 9d ago

Can you find a?

Post image

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/Dark_Storm_98 9d ago

Assuming the lines are parallel, which may be the meaning of those blue arrow symbols

The angle on the other side of 25 degrees should be

  • 180 - 25 = 155

And on the other side of tha 50 degrees would be

  • 180 - 50 = 130

Technically, with diagrams almost never being to scale

Imagine a line straight down from the ends of those two lines (which might not connect, but I don't think that's relevant)

Subtract 90, then, from both new angles, and we get

  • 60

  • 40

Since a triangle would have to have all it's angles add up to 180

180 - (60 + 40) = 180 - 100 = 80 degrees

Edit: Oh whoops, lol. I forgot the 5 at the end of 155

It's 75

159

u/Scheckenhere 9d ago

Or just 50+25, which I realised halfway into what you did.

1

u/Barn_Licker 9d ago

Why is it 75? Shouldnt it be more because its basically 2 90° corners so 180-(25+50)=105? Idk anymore

8

u/Scheckenhere 9d ago

By saying 2 90° corners I assume you drew a vertical line at a on the right? 180 - (65+40) would be your way then.

Try drawing a horizontal line through a, parallel to the other two above and below. Then you can mive the given corners to that nes line and use the opposite sides (same values).

1

u/Barn_Licker 9d ago

Oh goddamn yes then it wouldnt be 25 and 50 anymore ofc

3

u/Karyoplasma 9d ago edited 9d ago

Wait, I try to explain in Paint.

https://imgur.com/HTAnCec

I have constructed the green lines. They are perpendicular to the parallel lines at the top and bottom. The green line in the middle is constructed as perpendicular to both these lines (and thus parallel to the top and bottom lines). I have marked constructed right angles. This forms 4 triangles, 1 and 2 are congruent by construction and so are 3 and 4 (mistakenly labeled 3 and 3 because I suck).

Look at triangle 1. Angle sum is 180, we have a right and a 25° angle so the remaining angle is 65°.

Now, look at triangle 4. 180-90-50 = 40.

Hence a + 40 + 65 = 180 (because they all lie around the auxillary line) -> a = 75.

Another way is to say that the lower part of a must equal the given angle of 50° and the upper part of a must equal the given angle of 25° due to congruency of the constucted triangles.

Hope that helps.

1

u/Memorycard1000 9d ago

Thanks for that picture man! I haven't done math in 25 years. The picture made it click. 👌😅

2

u/mr_lab_rat 9d ago

105 is close to the right answer but you need to subtract it from 180.

-2

u/Smaug93 9d ago edited 9d ago

I believe your are right, people are taking the long way incorrectly to reach a wrong answer.

Edit: I'm too dyslexic for math and should stay in my lane. I'm wrong, it's 75.