[Tutor] move forward in arbitrary direction

[Michael Shulman]

Hello, I have what should be a basic math question, but I keep messing 
it up.

How do I code an equation so that when I have an object facing an 
arbitrary vector, pressing a key will make it move forwards in that 
direction?
(I understand all the key-based setup, it's just the equation for moving 
in the arbitrary vector direction that's got me stuck)

right now i can make something move up and down, or left and right, but 
if I want to rotate a triangle, then move it so that the 'tip' always 
points in the direction it's going to move, I get stuck.

the thing I have which doesn't work is something like
_____________________
vector = [0 0 0]

def specialKey(key,x,y):
    if key  == 'up':
       vector[0] = vector[0] + 1
_______________________
which I assume should be more like
--------------------------------
vector = [0 0 0]

def specialKey(key,x,y):
    if key  == 'up':
       vector[0] =  vector[0] * math.cos(something???)+ 1
       vector[2] =  vector[2] * math.sin(something??)+1
----------------------------------
Any help would be greatly appreciated!

ty, Mike