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Theorem 5.7 Theorem of each curve) Curve J of R2 is supplemented by Jordan River.

Two elements, the boundary of each element is j. R2 J? A whole infinity

Components and components? Represents R2 path connection and opening.

Let's start by showing each component. What about you? R2 is an open road. Contact. let

America ×2 is also locked as J compact in R2, so what about R2? J is open, so there is a small disk.

D is mainly in the first J, then you must connect from convex [D], so because of you.

[J]。 ? R2 is an inseparable part, we must have D America, so you are open. Connect as a local path for R2.

Therefore, any open subset of connections, such as U, is a path connection.

Through the compact room temperature j, the distance 2 J between points A and B is greater than Pythagoras.

Choose coordinates so that a = (? 1, 0) and b = 1, 0). So j is in the rectangle [? × 1、 1]

[? 2,2] = r, and the only score is in @R[J]. A and B. Let c = (0,2), d = 0,? 2)。

According to J lemma of cd segment, I am the second largest CD with 55 points.

Coordination. The point j of (a) and (b) is divided into two arcs, and we can say that the arc j is from a to.

Through Jc and other rice arcs. Let me click the cd \ Jc at least once.

Coordination.

Meet the Jd of each department, otherwise the two arcs Jd and cm+ld violate Lemma +you 550.

Let Kathy do ld \ Jd with j \ and learn Jd from the perspective of maximum second coordination.

At least two coordinates. Let x be the shooting range. The figure below illustrates this point.