1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    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!

Sine of sum and difference with 3 values

  1. Mar 9, 2012 #1
    1. The problem statement, all variables and given/known data

    sin (90 - θ + λ)

    = sin90cos(θ + λ) - cos90sin(θ + λ)

    = cos(θ + λ)

    The book says cos(θ - λ)

    So are we both right and if so how can I manipulate mine to look like the books answer.

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Mar 9, 2012 #2


    User Avatar
    Science Advisor
    Homework Helper

    hi afrocod! :smile:
    no, sin (90 - θ + λ) = sin (90 - (θ - λ))

    = sin90cos(θ - λ) - cos90sin(θ - λ) :wink:
  4. Mar 9, 2012 #3
    Ah my old friend Tim.

    I was surprised that 100's of people looked at this and nobody answered. I suspected this was a super easy question, as you just proved.

    Thank you very much.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook