azn099 wrote:

i really doubt i'll get a good answer here but meh i'll try.

anybody have any easy ways to memorize trigonometric identities? double-angle and half-angle identities are the ones i haven't got down yet. i know the pythagorean relationships and sum/difference identities already.

if u know the additon formulae then double angle shud not b a prob...

eg. sin(A+B) = sinAcosB+cosAsinB

then the double formulae would b...

sin2A = sin (A+A)

= sinAcosA+cosAsinA

= 2sinAcosA

sumhow i doubt i'm helping...