Simplify with Trigonometric Identities

  • Thread starter KleZMeR
  • Start date
  • #1
127
1

Homework Statement




I'm trying to simplify some trigonometric expressions, I'm attaching my work here. This comes from a famous physics problem i.e. the rod with two masses spinning on a circle. I've tried many times but I just can't get it. Any help on which identities to use would really help me.



Homework Equations



I'm attaching the simplified version, the 'answer'


The Attempt at a Solution



I'm attaching my work.
 

Attachments

  • photo (4).JPG
    photo (4).JPG
    50.8 KB · Views: 364
  • Screen Shot 2014-09-06 at 2.12.59 AM.png
    Screen Shot 2014-09-06 at 2.12.59 AM.png
    2 KB · Views: 364

Answers and Replies

  • #2
NascentOxygen
Staff Emeritus
Science Advisor
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Apply a couple of times sin2 x + cos2 x = 1
and your last line simplifies to the given answer
 
  • #3
127
1
Apply a couple of times sin2 x + cos2 x = 1
and your last line simplifies to the given answer

Yes, I looked at that identity, but there are 2 different angles in this problem, and also one of my last two terms is dø2*sin2Θ

Any direction on how to first apply the identity would also help?
 
  • #4
NascentOxygen
Staff Emeritus
Science Advisor
9,244
1,072
Take cos2 θ outside some brackets because it's a common factor.

And you'll see again, there's another common factor in two other terms to treat similarly.
 

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