The problem asks us to find the volume of a tetrahedron with vertices $A(2, -1, -3)$, $B(4, 1, 3)$, $C(3, 2, -1)$, and $D(1, 4, 2)$.

Geometry3D GeometryVolumeTetrahedronVectorsScalar Triple ProductCross Product
2025/6/15

1. Problem Description

The problem asks us to find the volume of a tetrahedron with vertices A(2,1,3)A(2, -1, -3), B(4,1,3)B(4, 1, 3), C(3,2,1)C(3, 2, -1), and D(1,4,2)D(1, 4, 2).

2. Solution Steps

The volume VV of a tetrahedron with vertices AA, BB, CC, and DD can be calculated using the scalar triple product of the vectors AB\vec{AB}, AC\vec{AC}, and AD\vec{AD}:
V=16(AB×AC)ADV = \frac{1}{6} |(\vec{AB} \times \vec{AC}) \cdot \vec{AD}|
First, find the vectors AB\vec{AB}, AC\vec{AC}, and AD\vec{AD}:
AB=BA=(42,1(1),3(3))=(2,2,6)\vec{AB} = B - A = (4-2, 1-(-1), 3-(-3)) = (2, 2, 6)
AC=CA=(32,2(1),1(3))=(1,3,2)\vec{AC} = C - A = (3-2, 2-(-1), -1-(-3)) = (1, 3, 2)
AD=DA=(12,4(1),2(3))=(1,5,5)\vec{AD} = D - A = (1-2, 4-(-1), 2-(-3)) = (-1, 5, 5)
Next, find the cross product AB×AC\vec{AB} \times \vec{AC}:
AB×AC=i^j^k^226132=i^(2263)j^(2261)+k^(2321)=i^(418)j^(46)+k^(62)=14i^+2j^+4k^=(14,2,4)\vec{AB} \times \vec{AC} = \begin{vmatrix} \hat{i} & \hat{j} & \hat{k} \\ 2 & 2 & 6 \\ 1 & 3 & 2 \end{vmatrix} = \hat{i}(2 \cdot 2 - 6 \cdot 3) - \hat{j}(2 \cdot 2 - 6 \cdot 1) + \hat{k}(2 \cdot 3 - 2 \cdot 1) = \hat{i}(4 - 18) - \hat{j}(4 - 6) + \hat{k}(6 - 2) = -14\hat{i} + 2\hat{j} + 4\hat{k} = (-14, 2, 4)
Now, find the scalar triple product (AB×AC)AD(\vec{AB} \times \vec{AC}) \cdot \vec{AD}:
(AB×AC)AD=(14,2,4)(1,5,5)=(14)(1)+(2)(5)+(4)(5)=14+10+20=44(\vec{AB} \times \vec{AC}) \cdot \vec{AD} = (-14, 2, 4) \cdot (-1, 5, 5) = (-14)(-1) + (2)(5) + (4)(5) = 14 + 10 + 20 = 44
Finally, find the volume VV:
V=16(AB×AC)AD=1644=446=223=713V = \frac{1}{6} |(\vec{AB} \times \vec{AC}) \cdot \vec{AD}| = \frac{1}{6} |44| = \frac{44}{6} = \frac{22}{3} = 7\frac{1}{3}

3. Final Answer

7137\frac{1}{3}

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