Yes I originally thought 90 but then noticed the absence of a right angle sign. Also 60+40=100 which means the last angle should be 80. Making that perpendicular 100/80
What a bunch of bullshit. Just draw it way off 90 if you don't want people to use a protractor. I calculated 125° because of this (but I'm happy I still got the right wrong answer, if that makes sense)
In my geometry classes, it's only 90 degrees if it's marked by a right angle marker. Otherwise, no matter how "right" it looks, if you assume before proving, it's on you.
this is a meme tho. i wanted to treat it like a "real life" problem where if i saw those obviously 90 degree corners, i would just say it's 90 because nowhere else in all my life outside of stupid schoolwork trick questions would that happen. which meant i got to the answer in a few seconds, which is a handy skill in real life.
You could potentially run into this or something very similar in cad when your sketches aren't fully defined yet. I've definitely ran into models that are slightly off square because someone missed a constraint much earlier in the timeline.
You start from left, and calculate them 1 by 1, based on the angles that you already know. It is quite simple actually, you just have to know they always add up to 180 (within triangle, and when you “split” the space over a straight line).
Nope. The value is "undefined". You don't have enough info to arrive at 135 - you are assuming that the bottom angle (sum of the angles that touch) is 180 degrees. Since there isn't a datum saying the bottom "line" is straight, nor does it say the triangle on the right is an isosceles triangle, it is impossible to solve.
I think assuming 2 line segments which make up a larger straight line segment to be parallel is generally accepted practice, and that would trump the angles that are drawn inaccurately.
Of course, it'd be better to put a hash through them both to indicate they're parallel, especially given the deceptively drawn most-likely-not-a-right-angle.
Even if it was a right angle, I think a second assumption is that the top left and bottom lines are equal length, which is also not stated.
I think there's just not enough information in this picture to calculate the angle, and it can only be determined by measuring. But the image also does not specify that it is drawn to scale.