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    Hi guys,

    Can someone please explain this to me?

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    I have never seen this before until the question that I just tried to do from the Edexcel textbook.

    I would have thought sinx=cos(x-(pi/2))?

    Thanks in advance!
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    (Original post by jasminetwine)
    Hi guys,

    Can someone please explain this to me?

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    I have never seen this before until the question that I just tried to do from the Edexcel textbook.

    I would have thought sinx=cos(x-(pi/2))?

    Thanks in advance!
    Remember that cos \theta = cos{-\theta} so both are true.
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    (Original post by SeanFM)
    Remember that cos \theta = cos{-\theta} so both are true.
    👌 thank you

    However, doesn't one shift the graph to the left and one to the right?
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    (Original post by jasminetwine)
    Hi SeanFM

    Thanks but unfortunately I can't read the symbols that you sent 🙈

    Are you able to show it to me some other way?

    Thanks so much
    He's saying cos(x) = cos(-x).
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    (Original post by Zacken)
    He's saying cos(x) = cos(-x).
    thank you

    However, doesn't one shift the graph to the left and one to the right?
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    (Original post by jasminetwine)
    thank you

    However, doesn't one shift the graph to the left and one to the right?
    If you let x = pi/2 - theta

    then -x = -(pi/2 - theta) = theta - pi/2.

    So cos(pi/2 - theta) = cos(theta - pi/2).
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    (Original post by Zacken)
    If you let x = pi/2 - theta

    then -x = -(pi/2 - theta) = theta - pi/2.

    So cos(pi/2 - theta) = cos(theta - pi/2).
    Thanks Zacken,

    I have followed the question through after what you said...

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    Would you be able to check my workings please?

    Attachment 547181547183

    I got 2 different answers, but the answers only have one 🙈

    Thank you very much!
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    (Original post by jasminetwine)
    Thanks Zacken,

    I have followed the question through after what you said...

    Name:  image.jpeg
Views: 55
Size:  13.2 KB

    Would you be able to check my workings please?

    Attachment 547181547183

    I got 2 different answers, but the answers only have one 🙈

    Thank you very much!
    You need to throw away one of the answers because it is given that -pi/2 < y < pi/2

    But pi/2 + arccos x > pi/2, so that doesn't work.

    So the other one is correct.
 
 
 
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