How to create a semicircle in the 3D graphing Simulator?

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Hi, I am currently doing a math final paper, and I need help creating half of a sphere in the 3D graphing simulator. I am trying to create a model of Einstein's theory of relativity, and I already have the plane for the fabric of spacetime. I need to add in half of a sphere, but I am unsure how to limit the domain of the sphere to only create half of it, not the whole thing. I know the command to create the whole sphere, I just need to know how to cut it in half, like a bowl.

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There's no direct command for half sphere's, cylinders etc, but you can use the Surface Command:

e.g.: Surface(sqrt(1-h²)*cos(α), sqrt(1-h²)*sin(α), h, α, 0°, 360°, h, 0, 1)

Of course you can shift the parameters of x, y and z to change the direction of the sphere.

The syntax of the command is Surface( <Expression>, <Expression>, <Expression>, <Parameter Variable 1>, <Start Value>, <End Value>, <Parameter Variable 2>, <Start Value>, <End Value> ) in which the expressions of the first three parameters of the commands define x, y and z.

chris

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