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Asking for a value of trigonometri

  1. Dec 26, 2004 #1
    I want to ask for what is the value for sin (180-theta/2) ?Thanks for anybody that spend time looking on my problem.
  2. jcsd
  3. Dec 26, 2004 #2
    Use the fact that sin (A - B) = sin Acos B - cos Asin B.
  4. Dec 26, 2004 #3


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    Well, first use the fact that sin(A+B)= sin(A)cos(B)+ cos(A)sin(B)!

    And, of course, sin(180)= 0 while cos(180)= -1 (I assume this is in degrees- you didn't actually say so).

    If you want this as a function of theta only (again, you didn't say what you really wanted), you will also need to know that sin(theta/2)= +/- √((1/2)(1- cos(theta)).
  5. Dec 26, 2004 #4
    Yeah, sorry that's what I meant :smile:. I thought it was obvious to then plug in the values of sin 180 and cos 180.
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