Chapter 14: Problem 1322
If a vertex of a triangle is \((1,1)\) and the mid-points of two sides through this vertex are \((-1,2)\) and \((3,2)\), then centroid of the triangle is (a) \([(1 / 3),(7 / 3)]\) (b) \([1,(7 / 3)]\) (c) \([-(1 / 3),(7 / 3)]\) (d) \([-1,(7 / 3)]\)
Short Answer
Expert verified
The centroid of the triangle is (1, 7/3), so the short answer is option (b) $[1,(\frac{7}{3})]$.
Step by step solution
01
Identify given information and notations
Given, a vertex of a triangle is A(1, 1) and the midpoints of two sides through this vertex are M1(-1, 2) and M2(3, 2). Let the other vertices of the triangle be B and C.
02
Find the coordinates of point B
Since M1 is the midpoint of AB, we can use the midpoint formula to find the coordinates of B:
Midpoint formula: \(\left( \frac{x_1 + x_2}{2}, \frac{y_1 + y_2}{2} \right)\)
Substitute the coordinates of point A(1,1) and M1(-1,2), we have:
\((-1, 2) = \left( \frac{1 + x_B}{2}, \frac{1 + y_B}{2} \right)\)
Now, solve for x_B and y_B:
\(x_B = 2 \times (-1) - 1 = -3\)
\(y_B = 2 \times 2 - 1 = 3\)
So, the coordinates of point B are (-3, 3).
03
Find the coordinates of point C
Similarly, since M2 is the midpoint of AC, we can use the midpoint formula to find the coordinates of C:
Substitute the coordinates of point A(1,1) and M2(3,2), we have:
\((3, 2) = \left( \frac{1 + x_C}{2}, \frac{1 + y_C}{2} \right)\)
Now, solve for x_C and y_C:
\(x_C = 2 \times 3 - 1 = 5\)
\(y_C = 2 \times 2 - 1 = 3\)
So, the coordinates of point C are (5, 3).
04
Calculate the centroid coordinates
The centroid of a triangle can be found by taking the average of its vertices' x-coordinates and y-coordinates:
Centroid: \(\left( \frac{x_A + x_B + x_C}{3}, \frac{y_A + y_B + y_C}{3} \right)\)
Substitute the coordinates of points A(1,1), B(-3,3), and C(5,3), we have:
Centroid: \(\left( \frac{1 - 3 + 5}{3}, \frac{1 + 3 + 3}{3} \right)\)
Simplifying the coordinates, we get:
Centroid: \(\left( \frac{3}{3}, \frac{7}{3} \right) = (1, \frac{7}{3})\)
The centroid of the triangle is (1, 7/3), so our answer is option (b).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Midpoint Formula
To understand the solution to a triangle centroid problem, it's essential to grasp the concept of the midpoint formula. The midpoint formula helps us find the middle point of a line segment in geometry. If you have two endpoints of a line segment, say
- Point 1: \(x_1, y_1\)
- Point 2: \(x_2, y_2\)
Coordinates of Triangle Vertices
Finding the coordinates of triangle vertices involves using known points and the midpoint formula. In problems where you're given a vertex and the midpoints of sides passing through this vertex, like
- Vertex A: \(1, 1\)
- Midpoints: \(M_1 = (-1, 2)\) and \(M_2 = (3, 2)\)
- For midpoint \(M_1\) (point A to B): Solve \(\left( \frac{1 + x_B}{2}, \frac{1 + y_B}{2} \right) = (-1, 2)\)
- For midpoint \(M_2\) (point A to C): Solve \(\left( \frac{1 + x_C}{2}, \frac{1 + y_C}{2} \right) = (3, 2)\)
Geometry Problems
Geometry problems often involve understanding spatial relationships between points and lines. In the case of triangles, aspects like vertex positioning, side calculations, and centroid determination are crucial.
- First, you need to visualize the triangle given specific points and midpoints.
- Next, solving for unknown vertices and ensuring each calculation checks out with known geometrical properties.
JEE Mathematics
JEE Mathematics requires a strong foundation in geometric principles to answer questions effectively.
- Your ability to apply basic formulas like the midpoint and centroid determination in problem-solving is tested.
- Conceptual clarity allows students to approach and solve complex triangle problems efficiently.