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Marion Walter 
Project Description Prerequisites Warm up Problems Hints Resources Teaching Notes Extension Problems Results

Warm Up Problems for Marion Walter's Theorem

1   Consider triangle a b c with its three sides trisected and lines drawn as indicated in Figure 3.

figure 3

Figure 3

(a)  What is the length of segment a prime c prime in terms of segment a c ?
(b)  Will these three lines always meet at one point as they appear to meet in the figure?  

2.  Suppose that the sides of  triangle a b c  in Figure 4 are divided into 5 equal parts and the division points that are closest to the vertices are connected as indicated in the figure below, with inner triangle triangle a prime b prime c prime formed from their intersection.

figure 4

Figure 4

(a)  What is the length  segment p q in terms of the length of segment a c?

(b)  What is the length of  segment a prime c prime in terms of the length of segment a c?

(c)  What is the area of triangle a prime b prime c prime in terms of the area of  triangle a b c ?

(d)  What are the areas of the diamond shaped regions at corners of these figures in terms of the area of triangle a b c ?

(e)  Find some other relationships in the figure.

3.   The equilateral triangle with thick lines in Figure 5 has area 1 and is rotated about its center 40 degrees and 80 degree to form the other two triangles.  What is the area of the inner nonagon?

figure 5

Figure 5

4.  (a)   Given four positive numbers a, b, c, and d, consider the points O(0,0), Q(a,c), R(b,d), and t of a plus b , c +d .  Find the area of parallelogram OQTR depicted in Figure 6.

figure 6

Figure 6

(b) You are given points A(0,0), B(1,0), and C(0,1),  and numbers a, b, c, and d such that a time d minus b time c is not zero.    Suppose that  A'B'C' is the triangle obtained by transforming each point on the original triangle by the rule  x y maps into the pair a x plus b y, c x plus d y.  How are the areas of triangle ABC and A'B'C' related in terms of a, b, c, and d?  Inititally you can think of the values of a, b, c, and d as positive, but your answer should be correct for all possible values.

5.  Consider triangle ABC with the following trisection points,
(1)  P on segment AB closest to B
(2) R on segment BC closest to C and
(3) Q on segment CA closest to A,
as in Figure 7.    If these points are connected by segments to the opposite vertices of the triangle, is the area of the inner triangle created by the segments related to the area of triangle ABC?

figure 7

Figure 7

We do not include results for this warm up problem on the Making Mathematics web site.

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