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    Express 8sin.pheta - 6cos.pheta in the form Rsin(pheta - alpha) where R>0 and 0<alpha<90

    I get r=2[sqroot]21
    But according to the mark scheme, r=10


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    (Original post by SDavis123)
    Express 8sin.pheta - 6cos.pheta in the form Rsin(pheta - alpha) where R>0 and 0<alpha<90

    I get r=2[sqroot]21
    But according to the mark scheme, r=10


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    I get R to equal 10...

    What did you do to get 2sqrt21?
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    (Original post by usycool1)
    I get R to equal 10...

    What did you do to get 2sqrt21?




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    You've made a basic arithmetic error at the end.

    \sqrt{8^2 + 6^2} \not= \sqrt{84}

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    (Original post by usycool1)
    You've made a basic arithmetic error at the end.

    \sqrt{8^2 + 6^2} \not= \sqrt{84}

    Ahhh ok lol, thanks


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