
William W. answered 08/01/23
Experienced Tutor and Retired Engineer
The centroid of the triangle is the center point that will balance the triangular plate. To find the centroid, you must draw at least two of the medians and find where they intersect (their intersection point is the centroid). A median connects a vertex and the midpoint of the opposite side,
Beginning at the vertex (5, 8), the opposite side has endpoints (2, 4) and (8, 3). The midpoint of that opposite side is found using the midpoint equation xmidpt = (x1 + x2)/2 = (2 + 8)/2 = 5 and ymidpt = (y1 + y2)/2 = (4 + 3)/2 = 3.5 so the midpoint is (5, 3.5). So the median is the line that connects the vertex (5, 8) and the midpoint (5, 3.5). Since these both have the same x-value, the line is x = 5.
Picking another vertex (2, 4), the opposite side has endpoints (5, 8) and (8, 3) making the midpoint (13/2, 11/2) or (6.5, 5.5). The median then is the line having points (2, 4) and (6.5, 5.5). To find that line, first get the slope: m = (y2 - y1)/(x2 - x1) = ((5.5 - 4)/(6.5 - 2) = 1.5/4.5 = 1/3. Using the point-slope form: y - y1 = m(x - x1) with m = 1/3 and (x1, y1) = (2, 4) we get the equation of the median line as:
y - 4 = (1/3)(x - 2)
Now, using the info we got from the first median line that x = 5, we can find the y-value of the intersection point:
y - 4 = (1/3)(5 - 2)
y - 4 = (1/3)(3)
y - 4 = 1
y = 5
So the centroid is the point (5, 5)