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Math Help - Using Trigonometric Identity

  1. #1
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    Using Trigonometric Identity

    a) Find the exact value of sin 135 by using sin (180 – 45)

    b) Find the exact value of sin 225 by using sin (270 – 45)
    b) Use the value of sin 225 found in b to find sin (–15) by using sin (225 – 240)
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  2. #2
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    Recall \sin (180-\theta) = \sin \theta

    so

    \sin 135 =  \sin (180-45) = \sin 45 = \dots
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  3. #3
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    Quote Originally Posted by pickslides View Post
    Recall \sin (180-\theta) = \sin \theta

    so

    \sin 135 = \sin (180-45) = \sin 45 = \dots


    but how i can solve part c of the question
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  4. #4
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    Are expected to solve the problem by using

    sin(A-B) = sinAcosB - cosAsinB ?
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