Final answer:
Similar triangles are triangles that have the same shape but not necessarily the same size. They have corresponding angles that are equal and corresponding sides that are proportional.
Step-by-step explanation:
In the given question, we are discussing the concept of similar triangles. Similar triangles are triangles that have the same shape but not necessarily the same size. They have corresponding angles that are equal and corresponding sides that are proportional.
For example, in the given scenario with the moon and the sun, the triangles HKD and KFD are congruent because they have the same angles and their corresponding sides are proportional. Similarly, the triangles GFC and AHD are congruent to the shaded ones.
Using this concept, we can determine that AC = 3R and AB = 3x, based on the given proportions.