Math Help - Tetrahedrom

1. Tetrahedrom

ABCD is a regular tetrahedron , its sides are of equal length . E and F are the midpoints of AB and CD respectively .

I am not sure what a tetrahedron is . Can someone show me the sketch ? Thanks !!

2. Hello,

And you'll get this, for example :

http://www.math.wichita.edu/history/...trahedron2.gif

(it's a 3-dimension structure)

3. Originally Posted by thereddevils
ABCD is a regular tetrahedron , its sides are of equal length . E and F are the midpoints of AB and CD respectively .

I am not sure what a tetrahedron is . Can someone show me the sketch ? Thanks !!
This is the continuation of the question .

Find the angle between

(a) the plane ABEF and the plane CDEF .

how can it be ABEF ?? Since E is the midpoint and AB ? I am confused .

4. Yeah, that's weird... defining the plane ABF would have been enough

Same for CDEF -> CDF...