Take the 2-minute tour ×  I want to draw a triangle with three
sides 5, 7, 9 and its incircle in geometry 3D. I used GeospacW.
I tried    • Draw a circle (T) has center origin and has radius
r=15/sqrt(11).   • Take a point A on (T) and draw a circle (C1)
has center A and has radius r=5.   • Find the intersection of
points between (T) and (C1), say one of them is B.   • Draw a
circle (C2) has center B and has radius 7.   • Find the
intersection of points between (T) and (C2), say one of them is
C.   • Draw the triangle ABC and its incircle.  enter image
description here  After drawing the triangle, I draw a pyramid
DABC with DC perpendicular to the plane (ABC) and
DC=\sqrt{33}/2.  enter image description here  share|improve
this question If you pre-compute all the coordinates in (x,y,z),
drawing it in 3D is easy. If you want to use geometric
construction, it is hard enough in 2D. In particular, the Tikz
through library uses 2D coordinates. –  John Kormylo Mar 30 at
5:04 In TikZ, we can define a coordinate with