Calculating Centroids of a Triangle: Why Do Formulas Switch?

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Discussion Overview

The discussion revolves around the calculation of centroids of a triangle, specifically addressing the confusion regarding the formulas used for determining the x and y coordinates. Participants explore the implications of triangle orientation on these calculations, examining both theoretical and practical aspects.

Discussion Character

  • Homework-related
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants state that the formula for the y-coordinate of a triangle's centroid is typically height/3, while the x-coordinate is calculated as 2/3 * base.
  • Others argue that in certain orientations, such as an upside-down triangle, the formula for the y-coordinate should be adjusted to 2/3 * height instead of height/3.
  • A participant questions whether the height refers to the longest side of the triangle, indicating a need for clarification on terminology.
  • There is a discussion about the orientation of the triangle affecting the calculation, with one participant noting that the base is at the top in their case, which complicates the use of standard formulas.
  • Another participant seeks clarification on how to calculate the x-coordinate, suggesting that the formulas may not be straightforward in this context.

Areas of Agreement / Disagreement

Participants express confusion over the switching of formulas for the y and x coordinates, indicating that there is no consensus on the correct approach due to the triangle's orientation. Multiple competing views remain regarding the appropriate formulas to use.

Contextual Notes

Participants highlight that the definitions of height and base may vary depending on the triangle's orientation, which affects the calculations. There is also uncertainty about the implications of using different sides as the base when calculating area.

CivilSigma
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Homework Statement


Hello. In class we learned how to calculate centroids of a triangle. For the y-coordinate we use the formula height/3 and for the x we use 2/3 * base

Homework Equations


In the diagram, If I want to calculate the y coordinate , I do 72 (which is the proposed height)/ 3 ; only to get y=24 which is incorrect.

It turns out that to find the y-coordinate in this case we must do 2/3*height. Why is that so? This is really confusing.
Why did the formulas to calculating 'y' and 'x' values switch?

Thank you for your time.
 

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sakonpure6 said:

Homework Statement


Hello. In class we learned how to calculate centroids of a triangle. For the y-coordinate we use the formula height/3 and for the x we use 2/3 * base

Homework Equations


In the diagram, If I want to calculate the y coordinate , I do 72 (which is the proposed height)/ 3 ; only to get y=24 which is incorrect.

It turns out that to find the y-coordinate in this case we must do 2/3*height. Why is that so?
Because the triangle is upside down. The "base" is at the top and you have to measure 1/3 of the way down.
sakonpure6 said:
This is really confusing.
Why did the formulas to calculating 'y' and 'x' values switch?

Thank you for your time.
 
But the height is still 72? and one more thing, when we say the height do we automatically pick the longest side of the triangle?

Edit: Okay I see what you mean now. If I do h/3 , I get 24 but that is from the top not the bottom of the plane.

However, how would you calculate the x-coordinate?
 
Last edited:
sakonpure6 said:
But the height is still 72? and one more thing, when we say the height do we automatically pick the longest side of the triangle?
Usually, what we call the base is at the bottom and horizontal, and the altitude or height is the vertical distance from the base to the opposite vertex. This triangle is oriented so that the base is at the top. When you calculate the area using A = (1/2) b * h, any side can be considered the base.
sakonpure6 said:
Edit: Okay I see what you mean now. If I do h/3 , I get 24 but that is from the top not the bottom of the plane.

However, how would you calculate the x-coordinate?
You have the formula in your first post.
 
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