The points A(2,4,-1) B(7,3,-8) C(6,10,-13) and D(1,11,-6) are the vertices of...?

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The points A(2,4,-1) B(7,3,-8) C(6,10,-13) and D(1,11,-6) are the vertices of quadrilateral ABCD.





a) Show that the quadrilateral is a rhombus





I found vectors AB, CD and AD, BC and determinated they are parralel and have the same magnitude. How do I determine the diagonal angles to show that they are 90 degrees?





b) Find the area of the rhombus


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The points A(2,4,-1) B(7,3,-8) C(6,10,-13) and D(1,11,-6) are the vertices of...?
i dont know about vectors but area of rhombus = 1/2*product of its diagonals

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