How many tetrahedrons are determined by nine points no four of which lie in the same plane? When i googled tetrahedrons , it is a 3D triangle . So now , i have no idea how that tetrahedrons will be drawn on the points. Please help me sir.
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So, when no four points lie on the same plane, any collection of $4$ points from the $9$ available points will give us a tetrahedron, right?
Hence, there are: $\binom94 =126$ ways.
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Ohh i see sir. But why 4 points? Isnt tetrahedron originally a triangle ? – Dave Jan 04 '18 at 11:13
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@Dave A tetrahedron is formed by four points right, a base triangle and an apex... – Jan 04 '18 at 11:30