how do you decide if the angles in a parallelopiped are 90 degrees?

If the parallelepiped is a rectangular solid, then it has right angles. The questions seems vague. Is there more to the question other than what you posted? @NyikoPearl

If all the angles are 90, then it will be a box.

the points A(1,3,2) B(3,-2,2) C(2,1,3) and D(1,-1,0) are given and the question are : a) does the base lie on a horzontal plane? b) decide if any angles in the parallelopiped are 90 degress c) find the co ordinates of the other four points please help this chapter is new to me and im struggling

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Is this vector calculus?

yes Wio

Okay, take every point and subtract point A from it.

That will give you 3 vectors for the parallelopiped.

Find those vectors first.

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