A triangle has corners at (3, 9 ), ( 7, -2), and ( 5, -9 )#. If the triangle is reflected across the x-axis, what will its new centroid be?

1 Answer
Jul 28, 2017

The new coordinates of the centroid is =(5,2/3)

Explanation:

Let the corners of the triangle be (x_1,y_1), (x_2,y_2) and (x_3,y_3)

The coordinates of the centroid are

C=((x_1+x_2+x_3)/2,(y_1+y_2+y_3)/3)

Here, we have (3,9), (7,-2), and (5,-9)

So,

The coordinates of the centroid are C=((3+7+5)/3,(9-2-9)/3)=(15/3,-2/3)=(5,-2/3)

The matrix of the reflection acrossthe x-axis is

M=((1,0),(0,-1))

Therefore,

The new coordinates of the centroid is

((x),(y))=((1,0),(0,-1))((5),(-2/3))=((5),(2/3))