Dumb geometry question

[EKS]

If you are given a figure depicting a triangle, and it is specified that the triangle in the figure is a right triangle, can you assume that the angle that looks like a right angle in the figure is the right angle?

[Arcadia]

No.  I have seen it stated in tests that the diagrams are not drawn to scale and the angles are not drawn accurately.

However you can write that down as an assumption in your solution to that problem. (I'm assuming free response question)

If it is a multiple choice question and only one angle looks like a right angle, than there is no choice but to assume given limited information.

[EKS]

This problem is a proof where I need to prove two triangles congruent.  I can easily do this (using what has been covered in the course so far) if I can assume that a particular angle is the right angle in each triangle.  But I can't figure out how to do it otherwise.

 

 

[Mom22ns]

They probably expect you to make that assumption.

[Julie of KY]

If you are told it is a right triangle, then I'd assume the one that looks 90 degree is the right angle. The biggest angle would have to be the 90 degree angle and the other two would be smaller and add up to 90 degrees.

[EKS]

If you are told it is a right triangle, then I'd assume the one that looks 90 degree is the right angle. The biggest angle would have to be the 90 degree angle and the other two would be smaller and add up to 90 degrees.

 

See, that's the logic I was thinking might work.  But then, it was drilled into my head in my own geometry class back in the dawn of time that just because something looks a certain way doesn't mean that it is that way.

[regentrude]

See, that's the logic I was thinking might work.  But then, it was drilled into my head in my own geometry class back in the dawn of time that just because something looks a certain way doesn't mean that it is that way.

 

I think that just means you may not assume that the angle that looks sort of like a right angle IS a right angle. But if the TELL you there is a right angle, it is reasonable to assume that that would be the one that looks like one. Anything else would be stupid problem design.

 

ETA: It would also be pretty obvious to you if you have the 'wrong" right angle, because then whatever relationship you were trying to prove would likely not work.

[Arcadia]

This problem is a proof where I need to prove two triangles congruent.  I can easily do this (using what has been covered in the course so far) if I can assume that a particular angle is the right angle in each triangle.  But I can't figure out how to do it otherwise.

 

I would just write down all the assumptions I have to make to solve the problem.  So in this case

 

Assumptions made:

Angle A of Triangle ABC is a right angle

Angle E of Triangle DEF is a right angle

 

I had examiners in engineering that wanted us to write down any assumptions we made if we need to make assumptions.