Question

Medians of a Triangle Quick Check 1 of 51 of 5 Items Question Use the image to answer the question. One way to prove that the medians of a triangle all meet at one point is by using arbitrary coordinates (0, 0) , (a, 0) , and (b, c) to represent the three vertices of the triangle. Drag and drop the missing pieces of each step to complete the proof that all three medians intersect at point P. (2 points) Put responses in the correct input to answer the question. Select a response, navigate to the desired input and insert the response. Responses can be selected and inserted using the space bar, enter key, left mouse button or touchpad. Responses can also be moved by dragging with a mouse. Step 1: Draw the three medians of the triangle. Draw each median so that it starts at a Response area and ends at the Response area of the opposite side. Step 2: Find the coordinates of each midpoint by taking the sum of the x-coordinates and dividing by 2 and taking the sum of the y-coordinates and dividing by 2. The midpoint between (0, 0) and (b, c) is (b2, c2) . The midpoint of (0, 0) and (a, 0) is (a2, 0) . The midpoint of (a, 0) and (b, c) is (a+b2, c2) . Step 3: Find the coordinates of P, the point where the medians appear to intersect, on each median. Use the formula Response area. Step 4: Find the coordinates of P on the median that starts at vertex (0, 0) and ends at midpoint (a+b2, c2) . 13(0, 0)+23(a+b2, c2)=(0, 0) + (a+b3, c3)=(a+b3, c3) Find the coordinates of P on the median that starts at vertex Response area and ends at midpoint (b2, c2) . 13(a, 0)+23(b2, c2)=(a3, 0)+(b3,c3)=(a+b3, c3) Find the coordinates of P on the median that starts at vertex (b, c) and ends at midpoint (a2, 0) . 13(b, c)+23(a2, 0)=(b3,c3)+(a3,0)=(a+b3,c3) Step 5: The coordinates of P on each median are Response area, which proves that the three medians of this generic triangle all intersect at the same point. Skip to navigation

Answer 1

To complete the proof that all three medians of a triangle intersect at a single point (the centroid), we can fill in the missing pieces step by step.

Step 1:

Draw the three medians of the triangle.

• Drag each median so that it starts at a vertex and ends at the midpoint of the opposite side.

Step 2:

Find the coordinates of each midpoint by taking the sum of the x-coordinates and dividing by 2 and taking the sum of the y-coordinates and dividing by 2.

• The midpoint between (0, 0) and (b, c) is \(\left(\frac{b}{2}, \frac{c}{2}\right)\).
• The midpoint of (0, 0) and (a, 0) is \(\left(\frac{a}{2}, 0\right)\).
• The midpoint of (a, 0) and (b, c) is \(\left(\frac{a + b}{2}, \frac{c}{2}\right)\).

Step 3:

Find the coordinates of P, the point where the medians appear to intersect, on each median. Use the formula.

• The formula for a point dividing a segment in the ratio m:n is given by \(\left(\frac{mx_2 + nx_1}{m+n}, \frac{my_2 + ny_1}{m+n}\right)\).

Step 4:

Find the coordinates of P on the median that starts at vertex (0, 0) and ends at midpoint \(\left(\frac{a + b}{2}, \frac{c}{2}\right)\):

• For median from (0, 0) to \(\left(\frac{a + b}{2}, \frac{c}{2}\right)\):
  • \(P = \frac{1}{3}(0, 0) + \frac{2}{3}\left(\frac{a + b}{2}, \frac{c}{2}\right) = \left(0 + \frac{2(a + b)}{6}, 0 + \frac{2c}{6}\right) = \left(\frac{a + b}{3}, \frac{c}{3}\right)\).

Find the coordinates of P on the median that starts at vertex (a, 0) and ends at midpoint \(\left(\frac{b}{2}, \frac{c}{2}\right)\):

• For median from (a, 0) to \(\left(\frac{b}{2}, \frac{c}{2}\right)\):
  • \(P = \frac{1}{3}(a, 0) + \frac{2}{3}\left(\frac{b}{2}, \frac{c}{2}\right) = \left(\frac{a}{3} + \frac{b}{3}, \frac{c}{3}\right) = \left(\frac{a + b}{3}, \frac{c}{3}\right)\).

Find the coordinates of P on the median that starts at vertex (b, c) and ends at midpoint \(\left(\frac{a}{2}, 0\right)\):

• For median from (b, c) to \(\left(\frac{a}{2}, 0\right)\):
  • \(P = \frac{1}{3}(b, c) + \frac{2}{3}\left(\frac{a}{2}, 0\right) = \left(\frac{b}{3} + \frac{a}{3}, \frac{c}{3}\right) = \left(\frac{a + b}{3}, \frac{c}{3}\right)\).

Step 5:

The coordinates of P on each median are \(\left(\frac{a + b}{3}, \frac{c}{3}\right)\), which proves that the three medians of this generic triangle all intersect at the same point.

By filling in these responses, we complete the proof that the three medians in a triangle meet at a single point, known as the centroid.