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Basic Geometry Question

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April 24, 2020, 03:46 PM
parallel
Basic Geometry Question
So... I've made a living from being a 3D modeler , a staff architect, and running my small drafting & design firm. Now I'll admit that, while I know enough math and geometry to do what I need to do, I'm certainly no math or geometry whiz.

With that said, here's the question; can a triangle be both an isosceles triangle AND an equilateral triangle at the same time?




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April 24, 2020, 03:49 PM
a1abdj
quote:
isosceles triangle AND an equilateral triangle at the same time?



Yes


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April 24, 2020, 03:50 PM
WaterburyBob
quote:
Originally posted by parallel:
So... I've made a living from being a 3D modeler , a staff architect, and running my small drafting & design firm. Now I'll admit that, while I know enough math and geometry to do what I need to do, I'm certainly no math or geometry whiz.

With that said, here's the question; can a triangle be both an isosceles triangle AND an equilateral triangle at the same time?

It depends on the definition that you use. One definition allows it.



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April 24, 2020, 03:50 PM
Aeteocles
Yes.
April 24, 2020, 03:50 PM
honestlou
I'm certainly rusty, but I'm pretty certain the answer is "no". By definition an isosceles triangle has exactly two equal sides- no more, no less. An equilateral triangle has three equal sides.
April 24, 2020, 03:51 PM
Otto Pilot
Depends on your definition of isosceles. I seem to recall that some say it is "exactly" two equal sides, some say "at least", so equilateral would be a special subset of isosceles.


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April 24, 2020, 04:18 PM
4MUL8R
https://mathworld.wolfram.com/IsoscelesTriangle.html


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April 24, 2020, 04:22 PM
c1steve
What about a 60-60-60 triangle. Two sides would be equal, and all angles are equal.


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April 24, 2020, 04:31 PM
DrDan
quote:
Originally posted by c1steve:
What about a 60-60-60 triangle. Two sides would be equal, and all angles are equal.


A triangle with all equal angles necessarily has all equal sides, and hence is equilateral.




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April 24, 2020, 04:39 PM
flashguy
My answer is "Yes". An equilateral triangle has 2 equal sides, so qualifies as isoceles, also--it is a special case. I have never seen a definition of isoceles triangle that would exclude an equilateral triangle from being one.

In a similar fashion, is a square a rectangle or a rhombus, and a rectangle a parallelogram? Yes, to all 3 questions--they are merely special cases.

flashguy




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April 24, 2020, 04:42 PM
stoic-one
I always understood an isosceles to be "at least 2 equal sides", so in theory, yes.


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April 24, 2020, 04:49 PM
Skins2881
quote:
Originally posted by DrDan:
quote:
Originally posted by c1steve:
What about a 60-60-60 triangle. Two sides would be equal, and all angles are equal.


A triangle with all equal angles necessarily has all equal sides, and hence is equilateral.


And also isosceles triangle as well.

Just as a square is a parallelogram as well as a rhombus and a rectangle.



Jesse

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April 24, 2020, 04:56 PM
DrDan
quote:
Originally posted by Skins2881:
quote:
Originally posted by DrDan:
quote:
Originally posted by c1steve:
What about a 60-60-60 triangle. Two sides would be equal, and all angles are equal.


A triangle with all equal angles necessarily has all equal sides, and hence is equilateral.


And also isosceles triangle as well.

Just as a square is a parallelogram as well as a rhombus and a rectangle.


Not disputing that, just pointing out that three equal angles is equivalent to three equal sides.




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April 24, 2020, 07:43 PM
nhtagmember
yes
April 24, 2020, 08:01 PM
V-Tail
All equilateral triangles are isosceles triangles.

Not all isosceles triangles are equilateral triangles.



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April 24, 2020, 08:04 PM
Skins2881
quote:
Originally posted by V-Tail:
All equilateral triangles are isosceles triangles.

Not all isosceles triangles are equilateral triangles.


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