1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Sum and Difference Formulas PROVE

  1. Nov 9, 2009 #1
    1. The problem statement, all variables and given/known data

    Given this formula


    prove this one

    Given this formula


    prove this one

    2. Relevant equations
    (difference and sum equations stated in the problem)

    3. The attempt at a solution
    I assume it's the same concept for both of them, i just don't know how to go about proving it to be true.
  2. jcsd
  3. Nov 9, 2009 #2


    Staff: Mentor

    a - b = a + (-b), so sin(a - b) = ?
  4. Nov 10, 2009 #3
    Like Mark44 said, use the fact that A - B = A + (-B).
    Hint: Sine is an odd function, which means that f(-x) = -f(x)
    2nd hint: Cosine is an even function, which means that f(-x) = f(x)

    That should do the trick.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook