Question:

If $ (3,\,\,3) $ is a vertex of a triangle and $ (-3,\,\,6) $ and $ (9,\,\,6) $ are the mid points of the two sides through this vertex, then the centroid of the triangle is

Updated On: Jun 2, 2024
  • $ (3,\,\,7) $
  • $ (1,\,\,7) $
  • $ (-3,\,\,7) $
  • $ (-1,\,\,7) $
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The Correct Option is A

Approach Solution - 1

Given, $ A=(3,3),E=(-3,6) $ and $ F=(9,6) $ Let $ B=({{x}_{1}},{{y}_{1}}) $ and $ C=({{x}_{2}},{{y}_{2}}) $
Then, $ \frac{{{x}_{1}}+3}{2}=-3,\,\,\,\,\,\,\,\,\,\,\,\,\frac{{{y}_{1}}+3}{2}=6 $
$ \Rightarrow $ $ {{x}_{1}}=-9,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,{{y}_{1}}=9 $
and $ \frac{{{x}_{2}}+3}{2}=9,\,\,\,\,\,\,\,\,\,\,\,\,\,\frac{{{y}_{2}}+3}{2}=6 $
$ \Rightarrow $ $ {{x}_{2}}=15,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,{{y}_{2}}=9 $
Now, centroid $ =\left( \frac{-9+15+3}{3},\frac{9+9+3}{3} \right) $
$ =(3,7) $
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Approach Solution -2

A triangle's centroid is the location inside the triangle where all of its medians meet or cross. Straight lines that connect a vertex to its opposite side and divide that side into two equal half are called medians. The triangle is divided into smaller, equal-sized triangles using a median as well. There are four locations when a triangle is concurrent.

Orthocentre

Incentre

Circumcentre 

Centroid

A triangle's centroid is always found inside the triangle's perimeter.

The centroid of the triangle is shown by point G in this instance. The centroid of a triangle always resides inside the triangle's perimeter, just like the incentre does. To get the centroid's coordinates, the section formula of coordinate geometry is used. A triangle's centroid, which coincides with its medians, always rests on a median and splits it 2:1. The centroid theorem refers to this.

The relative midpoints of the triangle's sides are denoted by D, E, and F. The triangle ABC's centroid is labeled G.

Following is a discussion of the characteristics of a triangle's centroid:

  • The point where all three of a triangle's medians meet or converge is known as the centroid.
  • The medians are split in half at the centroid in a 2:1 ratio. The centroid theorem is another name for this.
  • The most frequent point of concurrency inside a triangle is its centroid. Its significance in both mathematics and physics stems from the fact that it is the triangle's geometric core.
  • The centroid's coordinates satisfy the straight-line equations for the three medians since it is the intersection of all three of them. 
  • It is always situated inside a triangle's rim.

The coordinates of the three vertices of the triangle ABC are A(x1, y1), B(x2, y2), and C(x3, y3). D, E, and F are the respective midpoints of the sides BC, AC, and AB. G is the centroid.

Then the coordinates of the centroid of the triangle ABC are given as :

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Concepts Used:

Straight lines

A straight line is a line having the shortest distance between two points. 

A straight line can be represented as an equation in various forms,  as show in the image below:

 

The following are the many forms of the equation of the line that are presented in straight line-

1. Slope – Point Form

Assume P0(x0, y0) is a fixed point on a non-vertical line L with m as its slope. If P (x, y) is an arbitrary point on L, then the point (x, y) lies on the line with slope m through the fixed point (x0, y0) if and only if its coordinates fulfil the equation below.

y – y0 = m (x – x0)

2. Two – Point Form

Let's look at the line. L crosses between two places. P1(x1, y1) and P2(x2, y2)  are general points on L, while P (x, y) is a general point on L. As a result, the three points P1, P2, and P are collinear, and it becomes

The slope of P2P = The slope of P1P2 , i.e.

\(\frac{y-y_1}{x-x_1} = \frac{y_2-y_1}{x_2-x_1}\)

Hence, the equation becomes:

y - y1 =\( \frac{y_2-y_1}{x_2-x_1} (x-x1)\)

3. Slope-Intercept Form

Assume that a line L with slope m intersects the y-axis at a distance c from the origin, and that the distance c is referred to as the line L's y-intercept. As a result, the coordinates of the spot on the y-axis where the line intersects are (0, c). As a result, the slope of the line L is m, and it passes through a fixed point (0, c). The equation of the line L thus obtained from the slope – point form is given by

y – c =m( x - 0 )

As a result, the point (x, y) on the line with slope m and y-intercept c lies on the line, if and only if

y = m x +c