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Math Help - Find Value of Sin C

  1. #1
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    Find Value of Sin C

    In triangle ABC, sin (A + B) = 3/5.
    What is the value of sin C?
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    Quote Originally Posted by magentarita View Post
    In triangle ABC, sin (A + B) = 3/5.
    What is the value of sin C?
    In triangle ABC, C = 180^\circ - (A + B)^\circ

    So use the formula

    \sin{C} = \sin{[180^\circ - (A + B)^\circ]} = \sin{180^\circ}\cos{(A + B)^\circ} - \cos{180^\circ}\sin{(A + B)^\circ}

    and solve for \sin{C}.
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    Values for...

    Quote Originally Posted by Prove It View Post
    In triangle ABC, C = 180^\circ - (A + B)^\circ

    So use the formula

    \sin{C} = \sin{[180^\circ - (A + B)^\circ]} = \sin{180^\circ}\cos{(A + B)^\circ} - \cos{180^\circ}\sin{(A + B)^\circ}

    and solve for \sin{C}.
    I can plug and chug but what are the values of A and B? How do I find the values of A and B. Do I need the values of A and B?
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  4. #4
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    You don't need them.

    What does \sin{180^\circ} equal?

    Once you've found that, what does \sin{180^\circ}\cos{(A + B)^\circ} equal?

    What does \cos{180^\circ} equal?

    Since you're GIVEN the value of \sin{(A + B)^\circ}, what is \cos{180^\circ}\sin{(A + B)^\circ}?
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  5. #5
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    ok

    Quote Originally Posted by Prove It View Post
    You don't need them.

    What does \sin{180^\circ} equal?

    Once you've found that, what does \sin{180^\circ}\cos{(A + B)^\circ} equal?

    What does \cos{180^\circ} equal?

    Since you're GIVEN the value of \sin{(A + B)^\circ}, what is \cos{180^\circ}\sin{(A + B)^\circ}?
    I now understand what you mean.
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