this is a test where having lots of colors would be useful, because otherwise everything looks confusing.

leg of right triangle is geom mean
btwn piece of hypot next to it and length of full hypot

altitude is geom mean
btwn the 2 pieces of the hypot

trig functions
SOH CAH TOA. that is all.

law of sines
If you know an angle and the measure of opp side:
sinA/a = sinB/b = sinC/c

law of cosines
if you have info about all 3 sides or side angle side:
a^2 = b^2 + c^2 - 2bc(CosA)

vector
basically, a directed line segment
written like <x,y> (btw this is called component form)

magnitude
length of a vector
usually you can use pythagorean theorum to find this.

direction
the angle that the vector makes with a horizontal line. measured clockwise from x axis. usually involves N,S,E,W because Draz likes word problems a lot.

equal vectors
have same magnitude and direction

parallel vectors
have the same or opposite direction

resultant vector
the sum of 2 vectors. you just add them.

direction of resultant vector
tan^-1(x/y)