Question

Derive the trigonometric addition formula for sine:
sin(a + b) = sin a cos b + cos a sin b

Answer 1

Instead of expanding the thing out, you can also just apply the chain rule.\[\frac {d}{dx} \left[ \sin(a + b) \right] = \cos(a + b)\times \left[ \frac {da}{dx} + \frac {db}{dx} \right]\]

Answer 2

i think the question asks to come up with this identity... nothing to do with derivatives..

Answer 3

oh, lol. I misread :(

Answer 4

Try this:
http://www-spof.gsfc.nasa.gov/stargaze/Strig5.htm

Answer 5

wow, nasa...

Answer 6

NASA scientists do lots of stuff when they're bored...
http://apod.nasa.gov/htmltest/gifcity/e.1mil

But the information databases they create are very useful =)