Andrea
secondary (grade 10)
student
I am trying to find the centriod of a triangle. I have been given the three vertices of the triangle: A (25, 20), B (5, 40), and C (15, 30). I believe I calculated the correct midpoints: AB(E) (5, 5), BC(D) (5, 5), and AC(F) (15, 30). When I graphed these points I came up with the solution (5, 10), but I can't seem to write the answer out (equations of the lines, etc) correctly. Any help would be greatly appreciated!
Yours truly,
Andrea.

Andrea,
My diagram shows that E is the midpoint of CA, F is the midpoint of AB and D is the midpoint of BC.
I will write the equation of the line joining C and F, using the point slope form. The line is
(y  y_{1}) = m(x  x_{1})
(y  30) = m (x  15)
and
m = ^{(30  (30))}/_{(15  (15))} = ^{60}/_{30} = 2
Thus the equation of the line is
(y  30) = 2 (x  15) or
y = 2 x
Penny
