The Long River Sunsets the Japanese Yen depicts a red sun, which slowly falls below the river. At first, the round sun was far from the river, just like a circle and a line, and there was no intersection. Gradually, the red sun sets slowly, and when it first touches the river, only one intersection point forms the tangent relationship between the circle and the straight line. The red sun sets little by little, from the tangent of the circle to the intersection of the circle and the line. The intersection time is particularly long. The red sun is like a burning pomegranate swallowed up by the river, and darkness is quietly replacing the light. When the red sun was just swallowed up, it left the intersection point with the river, forming the tangent position relationship between the circle and the line. Then the sun quietly set, and in another unknown sky, it performed a bright journey of separation of circle and straight line.
The long river sets the yen reveals the positional relationship between the circle and the straight line, and shows us a wonderful geometric picture, which is the geometry in the poem.