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

Question

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

rogue · Answer

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

anonymous · Answer

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

rogue · Answer

oh, lol. I misread :(

rogue · Answer

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

anonymous · Answer

wow, nasa...

rogue · Answer

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 =)