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Thread: Trigonometric Identities

  1. August 8th 2010, 12:06 PM #1
    MATNTRNG
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    Trigonometric Identities

    What is equivalent to the value of sin(A+B) if sinA = cosB?

    I know the answer is 1. I just can't see how to get their using the trig identities.
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  2. August 8th 2010, 12:14 PM #2
    Archie Meade
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    Quote Originally Posted by MATNTRNG View Post
    What is equivalent to the value of sin(A+B) if sinA = cosB?

    I know the answer is 1. I just can't see how to get their using the trig identities.
    If sinA=cosB, then cosA=sinB also. Why?

    Expanding sin(A+B) then leads to

    cos^2B+sin^2B

    or

    sin^2A+cos^2A
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