ti89 hints
1. check cross products 
	crossP({1,2,3},{1,1,0})
		{-3,3,-1}
2. check dot products
	dotP({1,2,3},{-3,3,-1})
3. find equation of line of the interesection of two planes
	solve(x+y+z=3 and x+2*y-z=6,{x,y,z})
		x = -3*@4 and y = 2*@4+3 and z = @4
4. add/multiply vectors (lists actually)
	{1,2,3}+t*{2,-1, 3}
		{2*t+1, 2-t, 3*t+3}
5. length of a list, dim({1,2,3}) is 3
6. norm() doesn't work on a list, it needs a matrix, l_2 norm in n^2 space.
There is norm(list>mat({1,2,3}))  note "list>mat" is one command
7. CATALOG 3 jumps to the s section (while one needs) 
CATALOG alpha s alpha s (twice) strange.
8. x (times key) in 3D plots. Expanded/Unexpanded view.
9. | (key next to 7) changes 3D graphing mode.
10. +/- change animation speed (rotation)
11. 0 (zero key) resets
12. checking if two parameteric equations intersect.
method B: crossP the directions if zero there are parallel else dotP
with each intial point.