WEBVTT
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What is the intersection of planes 𝑀𝐴𝐵, 𝑀𝐵𝐶, and 𝑀𝐴𝐶?
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If we firstly consider the planes 𝑀𝐴𝐵 and 𝑀𝐵𝐶, it is clear from the diagram that the two planes intersect along the edge or line 𝑀𝐵.
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This is because 𝑀 and 𝐵 are common vertices of the two planes.
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Adding in the third plane 𝑀𝐴𝐶, we can see that this intersects the plane 𝑀𝐴𝐵 along the edge or line 𝑀𝐴.
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In a similar way, the plane 𝑀𝐴𝐶 intersects the plane 𝑀𝐵𝐶 along the edge or line 𝑀𝐶.
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However, we were asked for the intersection of all three planes: 𝑀𝐴𝐵, 𝑀𝐵𝐶, and 𝑀𝐴𝐶.
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Well, it is clear from the diagram that the only point or vertex, where all three planes intersect is point 𝑀 — vertex 𝑀.
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This is because the only common vertex of the three planes 𝑀𝐴𝐵, 𝑀𝐵𝐶, and 𝑀𝐴𝐶 is vertex 𝑀.