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Homework Help: Trig questions. Which ones are true.

  1. Oct 26, 2009 #1
    Which of the following are true?

    a) sin (theta − [pi/2]) = sin (theta)
    b) (sin [pi/3])(cos [pi/8]) = (sin [(3pi)/8])(cos [(3pi)/8])
    c) sin (theta + theta) = sin (2theta)
    d) (sin [2theta])/(sin [3theta]) = 2/3

    a) F
    b) F
    c) T
    d) T

    Tell me I got the right answers, please.
  2. jcsd
  3. Oct 26, 2009 #2


    Staff: Mentor

    Re: Trig.

    d is wrong. b looks right, but I would want to check it, just to be safe. The others are right.
  4. Oct 26, 2009 #3
    Re: Trig.

    If you have a graphing calculator you can graph both equation to verify they are equal.
  5. Oct 26, 2009 #4
    Re: Trig.

    a: pi/2 is just the phase shift. Will pi/2 make them out of phase?

    b: with no variable (Theta) plug and chug in the calculator unless you teacher wants you to prove?

    c: does does x+x=2x?

    d: when Theta =? or maybe I should say will it for any Theta.
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