To find the magnitude of dilation, we can use the formula for dilation with respect to the origin, which is defined as:
\[ A' = k \cdot A \]
where \(k\) is the dilation factor and \(A\) and \(A'\) are the coordinates of the points before and after dilation, respectively.
We can calculate the dilation factor \(k\) by taking a corresponding point from triangle ABC and triangle A'B'C'. Let's take point A as an example:
- The coordinates of A are (4, 2) and the coordinates of A' are (2, 1).
- We can find \(k\) by examining the relationship between the coordinates of A and A':
\[ k = \frac{A'_x}{A_x} = \frac{2}{4} = \frac{1}{2} \]
\[ k = \frac{A'_y}{A_y} = \frac{1}{2} = \frac{1}{2} \]
Since both the x and y coordinates give us the same dilation factor, we can confirm that the magnitude of dilation is consistent.
Now, let's apply the same calculations to another point, for instance point B:
- The coordinates of B are (-2, 6) and the coordinates of B' are (-1, 3).
Calculating \(k\) for B:
\[ k = \frac{B'_x}{B_x} = \frac{-1}{-2} = \frac{1}{2} \]
\[ k = \frac{B'_y}{B_y} = \frac{3}{6} = \frac{1}{2} \]
This also confirms that \(k = \frac{1}{2}\).
Finally, we can check point C:
- The coordinates of C are (-6, -4) and the coordinates of C' are (-3, -2).
Calculating \(k\) for C:
\[ k = \frac{C'_x}{C_x} = \frac{-3}{-6} = \frac{1}{2} \]
\[ k = \frac{C'_y}{C_y} = \frac{-2}{-4} = \frac{1}{2} \]
Once again, both the calculations yield \(k = \frac{1}{2}\).
Therefore, the magnitude of dilation is:
\[ \boxed{\frac{1}{2}} \]