Proving the Centroid of ABC Triangle

In summary, the problem asks to prove that point I, which divides angle BAC into two equal parts, is the centroid of the triangle formed by points B, AC and the triangle formed by points C, AB. The Pythagorean theorem and the sine formula can be used to prove that IG=IS.
  • #1
Andrax
117
0

Homework Statement



let ABC be a triangle where I divides angle BAC(angle A) => BAI=IAC
Prove that I is the centroid of (B,AC)and (C,AB)

Homework Equations


i think phitagors wil come in handy but don't know how to use it


The Attempt at a Solution


let ac = a and AB = b
aIB+bIC=0 (vectors)
aIC+aCB+bIC=(a+b)IC+aCB=..
 
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  • #2
Did you copy the problem statement 1:1? It looks strange, phrased like that:

- the centroid is a point in a geometric shape, I would expect to see the triangle here. But (B,AC) and (C,AB) are strange ways to refer to a triangle
- I has to lie on the bisection of angle BAC, but nothing else is given. It could be anywhere, far away from the centroid.
Andrax said:
phitagors
Pythagoras?

I don't understand your notation at (3.).
 
  • #3
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  • #4
I think this problem statement does not make sense.
 
  • #5
It does... Dunno what I'm doing wrong
 
  • #6
Hi Andrax! :smile:

Just use the sine formula. :wink:

(mfb, i think it means the centroid of a weight AC at B and a weight AB at C :biggrin:)
 
  • #7
tiny-tim said:
Hi Andrax! :smile:

Just use the sine formula. :wink:

(mfb, i think it means the centroid of a weight AC at B and a weight AB at C :biggrin:)

thank you , with the' use of cos and sin i managed to prove that IG=IS anyway in class we used sin and cos + the S of the triangles
 
  • #8
tiny-tim said:
(mfb, i think it means the centroid of a weight AC at B and a weight AB at C :biggrin:)
Ah, that makes sense.
We still need the requirement that I is on (BC), however.
 

Related to Proving the Centroid of ABC Triangle

1. What is the centroid of a triangle?

The centroid of a triangle is the point of intersection of the three medians of the triangle. A median is a line segment that connects a vertex of the triangle to the midpoint of the opposite side.

2. How is the centroid of a triangle calculated?

The centroid of a triangle can be calculated by finding the average of the x-coordinates and the average of the y-coordinates of the three vertices of the triangle. This will give the coordinates of the centroid (x̄, ȳ).

3. Why is proving the centroid of a triangle important?

Proving the centroid of a triangle is important because it is a fundamental concept in geometry and is used in many geometric proofs and constructions. It also has practical applications in engineering and architecture.

4. What is the significance of the centroid in a triangle?

The centroid is significant because it is the center of mass of the triangle. This means that if the triangle is cut out of a uniform material, the centroid is the point where it would balance perfectly on a pin. The centroid is also the center of the inscribed circle in a triangle.

5. How can the centroid of a triangle be proved?

The centroid of a triangle can be proved using various methods, such as using the properties of medians, vectors, or coordinates. One common method is by using the Triangle Midsegment Theorem, which states that the segment connecting the midpoints of two sides of a triangle is parallel to the third side and half its length. By using this theorem and the properties of parallel lines, the centroid can be proved.

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