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submitted 1 month ago by sjmarf@sh.itjust.works to c/whitepeopletwitter@sh.itjust.works

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[-] TheGrandNagus@lemmy.world 218 points 1 month ago* (last edited 1 month ago)

What a deviously misleading diagram.

The triangle on the left isn't actually a right angle triangle, as the other angles add to 100°, meaning the final one is actually 80°, not 90°.

Therefore the triangle on the right also isn't a right angle triangle. That corner is 100°.

100+35=135°. 180-135=45°. So that's 45° for the top angle.

X = the straight line of the joined triangles (180°) - the top angle of the right triangle (45°). 180-45=135°

X is 135°, not the 125° it initially appears to be.

[-] greyfox@lemmy.world 69 points 1 month ago

It also doesn't say that the line on the bottom is straight, so we have no idea if that middle vertex adds up to 180 degrees. I would say it is unsolvable.

[-] TheOakTree@lemm.ee 29 points 1 month ago

This is what I was thinking. The image is not to scale, so it is risky to say that the angles at the bottom center add up to 180, despite looking that way. If a presented angle does not represent the real angle, then presented straight lines might not represent real lines.

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[-] GoodEye8@lemm.ee 26 points 1 month ago

I used to have teacher who deliberately made disproportionate diagrams. His reasoning was that people trust too much what their eyes see and not enough what the numbers tell them. He would've loved that diagram.

[-] frezik@midwest.social 18 points 1 month ago

The person who made it needs this:

https://xkcd.com/169/

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[-] tpihkal@lemmy.world 14 points 1 month ago

Leave it to the Grand Nagus to spot a clever ruse.

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[-] jordanlund@lemmy.world 12 points 1 month ago

I looked at that "90°" angle and went "that doesn't look right..."

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[-] Habahnow@sh.itjust.works 64 points 1 month ago

All these people saying its 135 are making big assumptions that I think is incorrect. There’s one triangle (the left one) that has the angles 40, 60, 80. The 80 degrees is calculated based on the other angles. What's very important is the fact that these triangles appear to have a shared 90 degree corner, but that is not the case based on what we just calculated. This means the image is not to scale and we must not make any visual assumptions. So that means we can’t figure out the angles of the right triangle since we only have information of 1 angle (the other can’t be figured out since we can’t assume its actually aligned at the bottom since the graph is now obviously not to scale).

Someone correct me if I'm wrong.

[-] Brosplosion@lemm.ee 56 points 1 month ago

135 is correct. Bottom intersection is 80/100, 180-35-100 = 45 for the top of the second triangle. 180 - 45 = 135

[-] Leate_Wonceslace@lemmy.dbzer0.com 26 points 1 month ago

Mathematician here; I second this as a valid answer. (It's what I got as well.)

[-] PresidentCamacho@lemm.ee 14 points 1 month ago

Random guy who didn't sleep in middle school here: I also got the same answer.

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[-] TheOakTree@lemm.ee 14 points 1 month ago

You're making the assumption that the straight line consisting of the bottom edge of both triangles is made of supplementary angles. This is not defined due to the nature of the image not being to scale.

[-] NoMoreLurkingToo@startrek.website 22 points 1 month ago

Unless there are lines that are not straight in the image (which would make the calculation of x literally impossible), the third angle of the triangle in the left has to be 80°, making the angle to its right to be 100°, making the angle above it to be 45°, making the angle above it to be 135°. This is basic trigonometry.

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[-] brisk@aussie.zone 39 points 1 month ago

This is a standard way to draw geometric proofs, it's not at all unreasonable to assume straight lines alongside unrepresentative angles. It's certainly still an assumption, but a conventional one.

[-] qarbone@lemmy.world 21 points 1 month ago

I mean, the assumption shouldn't be anything about scale. It should be that we're looking at straight lines. And if we can't assume that, then what are we even doing.

But, assuming straight lines, given straight lines you find the other side of an intersecting line because of complements.

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[-] dragonfucker@lemmy.nz 49 points 1 month ago

135

[-] PresidentCamacho@lemm.ee 67 points 1 month ago* (last edited 1 month ago)

It pisses me off to no end that what is CLEARLY shown as a 90degree angle is not in fact 90deg, I hate it when they do that.

Also I will sadly admit this can teach people lessons about verifying the information themselves.

^GrumbleGrumbleGrumble....^

[-] yannic@lemmy.ca 13 points 1 month ago* (last edited 1 month ago)

I get you, but it doesn't clearly indicate the angle in the middle at the base as much as it suggestively waggles its eyebrows towards 90⁰, it could just as easily be 89.9999999999999⁰, although upon zooming in, you can see the line does shift one pixel over on its way up. You simply can't trust any of the angles as 90⁰ unless it's got the ∟ symbol (that's the official unicode) or you've measured them yourself, and with that one pixel off-set, it's decidedly not 90⁰. That's why you have to do the math.

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[-] ngwoo@lemmy.world 13 points 1 month ago

Geometry diagrams in math problems should never be assumed to be to scale

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[-] Skullgrid@lemmy.world 46 points 1 month ago

trash diagram too, the 90 degree looking center angle is actually 80 on the left, 100 on the right.

180 - (100 + 35) = y

x = 180 -y

I can't be assed to do the simple math

[-] SomeoneSomewhere@lemmy.nz 33 points 1 month ago

135°.

The non-right-angle is downright cheeky.

[-] FunderPants@lemmy.ca 10 points 1 month ago

Oh my god , those jerks. Lol

[-] tigeruppercut@lemmy.zip 17 points 1 month ago

trash diagram too

A lot of those standardized tests like SAT or GRE like to put those in (or at least they used to) on purpose. It wasn't that they couldn't render the diagrams correctly, instead they were checking for people making assumptions with information that wasn't given. To be somewhat fair I seem to recall a disclaimer that they weren't necessarily drawn accurately.

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[-] NigelFrobisher@aussie.zone 17 points 1 month ago

I like that all the comments are people discussing the diagram.

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[-] FundMECFSResearch@lemmy.blahaj.zone 17 points 1 month ago

135

[-] tyler@programming.dev 14 points 1 month ago

Right one does not depend on the left one. 3rd dimension for the win!

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[-] RandomStickman@fedia.io 13 points 1 month ago

C'man there's totally a 1px shift on the line. You can't just assume it's a right angle.

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[-] AVincentInSpace@pawb.social 11 points 1 month ago

The answer is 125 degrees but the triangle on the left has 190 degrees in it

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[-] MrQuallzin@lemmy.world 10 points 1 month ago* (last edited 1 month ago)

125°

Edit: Damn I'm getting roasted for getting it wrong. I totally am wrong, but when I've been awake for only 5 minutes that's bound to happen XD

[-] Skasi@lemmy.world 8 points 1 month ago

It's a trap. The drawing is misleading. If the left triangle already has 60° and 40° then only 80° remains. Meaning there's no right angle. The vertical line should be leaning to the left slightly. The correct answer is 135°.

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[-] billwashere@lemmy.world 10 points 1 month ago

Either this is drawn wrong or they broke geometry

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[-] switchboard_pete@fedia.io 10 points 1 month ago

the answers here assume that the base is a continuous, straight line

given one of the angles on the left triangle is a right angle on the diagram, but 80 if you calculate it, you can't assume that

[-] brisk@aussie.zone 11 points 1 month ago

This is a standard way to draw geometric proofs, it's not at all unreasonable to assume straight lines and unrepresentative angles.

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[-] batucada@lemmy.world 9 points 1 month ago

Doing 5th grade math makes me feel like a fucking genius. Cant believe I figured it out tbh

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this post was submitted on 08 Oct 2024

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