this post was submitted on 08 Oct 2024
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[–] [email protected] 56 points 1 month ago (3 children)

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

[–] [email protected] 1 points 1 month ago

When you're finding the outside angle along the line of a triangle you don't need the inside angle tied to that outside angle if you have the other two inside angles since both straight lines and triangles total to 180 degrees.

[–] [email protected] 26 points 1 month ago (1 children)

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

[–] [email protected] 14 points 1 month ago (1 children)

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

[–] [email protected] 7 points 1 month ago

Random woman who didn't sleep very well last night. I got a different answer, then thought about it for 10 more seconds and then got 135.

(No I didn't assume the right angle, my mistake was even dumber. I need a nap.)

[–] [email protected] 14 points 1 month ago (1 children)

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.

[–] [email protected] 23 points 1 month ago (3 children)

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.

[–] [email protected] 0 points 1 month ago

which would make the calculation of x literally impossible

Yes.

But that doesn't mean that line must be straight. It just means if it isn't, you can't derive x.