If the centroid and a vertex of an equilateral triangle are 2,3 and 4,3
Answers
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The other coordinates of the triangle are (1, 3+√3) and (1, 3-√3)
Given,
Let the triangle under consideration be ΔABC
The centroid of the triangle, G = (2,3)
One vertex of the triangle, A = (4,3)
To Find,
The other two vertices of the triangle (B=? and C=?)
Solution,
Consider the triangle ΔABC
Let AD be the median of the triangle.
We know that the centroid G divides the median of a triangle in the ratio of 2:1
⇒ AG/GD = 2/1
⇒ AG = 2GD
Now let the coordinates of D be (x,y)
Then, G = ((2x+4)/3, (2y+3)/3)
⇒ (2,3) = ((2x+4)/3, (2y+3)/3)
⇒ 2 = (2x+3)/3 and 3 = (2y+3)/3
⇒ 6 = 2x+3 and 9 = 2y+3
⇒ 2x = 6-3 and 2y = 9-3
⇒ x = 3/2 and y = 3
Therefore, the vertex D is (3/2, 3)
Now, As ΔABC is an equilateral triangle, so median is the same as the altitude of the triangle.
⇒ tan 60° = AD/BD (each angle in an equilateral triangle is 60°)
⇒ √3 = 3/BD
⇒ BD = 3/√3
⇒ BD = √3
Now, A(4,3), G(2,3), and D(1,3) lie on y = 3, and BC is perpendicular to AD.
⇒ B, C, and D have the same x-coordinate = 1
Then √((1−1)² + (y−3)²) = √3
⇒ (y-3)² = 3
⇒ y = 3 ± √3
Therefore, the other coordinates of the triangle are B(1, 3+√3) and C(1, 3-√3)
Correction in question: If the centroid and a vertex of an equilateral triangle are (2,3) and (4,3), then find the other coordinates of the triangle.
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