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    I'm rather stuck on this question.

    given that cosec C = 7, sin²D = 0.5 and tan²E = 4, find the possible values of cot C, sec D and cosec E, giving your answers in exact form.

    *******************************


    I started by doing:

    cosec C = 7

    1/(sin C) = 7

    (1/7) = sin C

    But then got stuck about here.
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    (Original post by 2776)
    I'm rather stuck on this question.

    given that cosec C = 7, sin²D = 0.5 and tan²E = 4, find the possible values of cot C, sec D and cosec E, giving your answers in exact form.

    *******************************


    I started by doing:

    cosec C = 7

    1/(sin C) = 7

    (1/7) = sin C

    But then got stuck about here.
    Poor 2776, nobody has helped him on his maths question yet.
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    :confused: Do you do edexcel p3? not seen anything like that before sorry.
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    (Original post by Absolution)
    :confused: Do you do edexcel p3? not seen anything like that before sorry.
    OCR
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    (Original post by 2776)
    OCR
    ah that would explain it, i haven't covered that sort of equation before and hopefully won't have too good luck !
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    1 + cot^2 = cosec^2, so
    cot^2 C = 48 etc
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    (Original post by 2776)
    I'm rather stuck on this question.

    given that cosec C = 7, sin²D = 0.5 and tan²E = 4, find the possible values of cot C, sec D and cosec E, giving your answers in exact form.

    *******************************


    I started by doing:

    cosec C = 7

    1/(sin C) = 7

    (1/7) = sin C

    But then got stuck about here.
    i got cot C=sqrt(48),sec D=sqrt(2) and -sqrt(2),cosec E=sqrt(5)/2.
    There are more asumming postive and negative roots,also wot are the domains of the angles C, D, E?
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    (Original post by IntegralAnomaly)
    i got cot C=sqrt(48),sec D=sqrt(2) and -sqrt(2),cosec E=sqrt(5)/2.
    There are more asumming postive and negative roots,also wot are the domains of the angles C, D, E?
    No domains mentioned. I think it is only wanting to ask for the first few answers. Cheers, got it now.
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    (Original post by 2776)
    I'm rather stuck on this question.

    given that cosec C = 7, sin²D = 0.5 and tan²E = 4, find the possible values of cot C, sec D and cosec E, giving your answers in exact form.
    cosec C = 7

    squaring gives:

    cosec^2 C = 49

    using identity gives:

    1 + cot^2 C = 49

    rearranging gives:

    cot^2 C = 48

    square rooting gives:

    cot C = plus or minus √48 = plus or minus 4√3


    sin^2 D = 0.5

    using identity gives:

    1 - cos^2 D = 0.5

    rearranging gives:

    cos^2 D = 0.5

    square rooting gives

    cos D = plus or minus 1/√2

    taking reciprocal:

    sec D = plus or minus √2


    I'll have to think about the third one.
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    its really the E one taht I'm stuck on, tried sec²E = 5, then sin²E/cos²E = 4, but not really going anywhere.
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    (Original post by hornblower)
    cosec C = 7

    squaring gives:

    cosec^2 C = 49

    using identity gives:

    1 + cot^2 C = 49

    rearranging gives:

    cot^2 C = 48

    square rooting gives:

    cot C = plus or minus √48 = plus or minus 4√3


    sin^2 D = 0.5

    using identity gives:

    1 - cos^2 D = 0.5

    rearranging gives:

    cos^2 D = 0.5

    square rooting gives

    cos D = plus or minus 1/√2

    taking reciprocal:

    sec D = plus or minus √2


    I'll have to think about the third one.
    for the third 1 tanE=2(im nt taking the negative 1)
    therefore sinE=2/(sqrt(5)) (using a right angled triangle with angle E)
    ergo cosec E =sqrt(5)/2
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    (Original post by 2776)
    I'm rather stuck on this question.

    given that cosec C = 7, sin²D = 0.5 and tan²E = 4, find the possible values of cot C, sec D and cosec E, giving your answers in exact form.

    *******************************


    I started by doing:

    cosec C = 7

    1/(sin C) = 7

    (1/7) = sin C

    But then got stuck about here.
    For cosec(E), if you take the reciprocal of tan^2(E) to find cot^2(E) = 1/4, then use the identity;

    cosec^2(E) = 1 + cot^2(E)

    So cosec^2(E) = 5/4 and cosec(E) = (sqrt5)/2, as the person above correctly stated.

    Ben
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    (Original post by Ben.S.)
    For cosec(E), if you take the reciprocal of tan^2(E) to find cot^2(E) = 1/4, then use the identity;

    cosec^2(E) = 1 + cot^2(E)

    So cosec^2(E) = 5/4 and cosec(E) = (sqrt5)/2, as the person above correctly stated.

    Ben
    oh yes thats a much better way
 
 
 
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