Math Is Fun Forum

beem

Member

Registered: 2012-05-25

Posts: 1

Right Pyramids

Many definitions indicate that in order to be a right pyramid, the base must be regular.  So my question is:
Is a pyramid that has a rectangle as its base and the vertex directly above the intersection of the rectangle`s diagonals considered a RIGHT pyramid?

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Right Pyramids

Hi beem;

Welcome to the forum.

I think a pyramid can have a base shape that is any polygon. If the apex is directly over the centroid of the base then it is a right pyramid.

http://mathworld.wolfram.com/RightPyramid.html

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,649

Re: Right Pyramids

hi beem,

Welcome to the forum.

Yes, the pyramid you describe is a 'right' one.

In a prism there is an axis, with the cross section of the prism taken at any point on the axis at right angles to it.

A similar thing applies to pyramids except that a pyramid that 'leans over' may still be consider a pyramid.

If the axis is at right angles to the base, then it is called a right pyramid.  So the word 'right' is being used because of the right angle.  I think a pyramid that is not right is called skew.  LATER EDIT:  Ok I give in.  Everyone else but me calls it oblique! (eg mathswords and MathsIsFun say it is called oblique)

see also http://www.mathsisfun.com/geometry/pyramids.html

non right pyramid in picture

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob