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!

John Taylor Classical Mechanics Chapter 1 Problem 22

  1. Aug 23, 2013 #1
    1. The problem statement, all variables and given/known data
    The two vectors a and b lie in the xy plane and make angles (alpha and beta) with the x axis. a. by evaluating a dot b in two ways prove the well known trig identity cos(alpha-beta)=cosalphacosbeta +sinalphasinbeta


    2. Relevant equations
    adotb=abcostheta=axbx+ayby


    3. The attempt at a solution
    Could not really come to the proper set-up.
     
  2. jcsd
  3. Aug 23, 2013 #2

    ehild

    User Avatar
    Homework Helper
    Gold Member

    How are the x,y components of a vector related to the angle they make with the x axis?

    ehild
     
  4. Aug 23, 2013 #3
    the angle they make is in the problem; the cos of the difference of the angles equals that result. i just cud not go from the dot product to that.
     
  5. Sep 6, 2013 #4

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    hi karmonkey98k! :smile:

    start with a = |a|cosαi + |a|sinαj :wink:
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: John Taylor Classical Mechanics Chapter 1 Problem 22
Loading...