Finding the Centroid of a Triangle in 3D Space

The question asks us to find the centroid of a triangle given the coordinates of its three vertices in 3D space.

The vertices of the triangle are given as:

• A: (2, -3, 3)
• B: (5, -3, -4)
• C: (2, -3, -2)

The centroid of a triangle is the point where the three medians of the triangle intersect. A median of a triangle is a line segment joining a vertex to the midpoint of the opposite side.

For a triangle with vertices \(A(x_1, y_1, z_1)\), \(B(x_2, y_2, z_2)\), and \(C(x_3, y_3, z_3)\) in 3D space, the coordinates of the centroid \(G(x, y, z)\) are given by the formula:

\[ G = \left( \frac{x_1 + x_2 + x_3}{3}, \frac{y_1 + y_2 + y_3}{3}, \frac{z_1 + z_2 + z_3}{3} \right) \]Using the given coordinates:

• \(x_1 = 2, y_1 = -3, z_1 = 3\)
• \(x_2 = 5, y_2 = -3, z_2 = -4\)
• \(x_3 = 2, y_3 = -3, z_3 = -2\)

Now, let's calculate the coordinates of the centroid G:

Calculating the x-coordinate:

\[ x = \frac{x_1 + x_2 + x_3}{3} = \frac{2 + 5 + 2}{3} = \frac{9}{3} = 3 \]Calculating the y-coordinate:

\[ y = \frac{y_1 + y_2 + y_3}{3} = \frac{-3 + (-3) + (-3)}{3} = \frac{-9}{3} = -3 \]Calculating the z-coordinate:

\[ z = \frac{z_1 + z_2 + z_3}{3} = \frac{3 + (-4) + (-2)}{3} = \frac{3 - 4 - 2}{3} = \frac{3 - 6}{3} = \frac{-3}{3} = -1 \]

So, the coordinates of the centroid are (3, -3, -1).

Let's compare this result with the given options:

• Option 1: (-3, 3, -1)
• Option 2: (3, -3, -1)
• Option 3: (3, 1, -3)
• Option 4: (-3, -1, -3)

The calculated centroid (3, -3, -1) matches Option 2.

Revision Table: Centroid Calculation Summary

Additional Information on Triangle Centers

Besides the centroid, there are several other important points associated with a triangle. These are often referred to as triangle centers:

• Incenter: The intersection point of the three angle bisectors. It is the center of the inscribed circle (incircle) of the triangle.
• Circumcenter: The intersection point of the three perpendicular bisectors of the sides. It is the center of the circumscribed circle (circumcircle) that passes through all three vertices.
• Orthocenter: The intersection point of the three altitudes of the triangle. An altitude is a line segment from a vertex perpendicular to the opposite side.

The centroid, orthocenter, and circumcenter are collinear (lie on the same straight line) in any triangle. This line is known as the Euler line.