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Math Help - Trigs

  1. #1
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    Trigs

    how do i solve this? i'm suppose for solve x
    (Cotx)(Cosx)= Cosx
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  2. #2
    Forum Admin topsquark's Avatar
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    Quote Originally Posted by imthatgirl View Post
    how do i solve this? i'm suppose for solve x
    (Cotx)(Cosx)= Cosx
    cot(x)~cos(x) = cos(x)

    cot(x)~cos(x) - cos(x) = 0

    (cot(x) - 1)~cos(x) = 0

    So either
    cot(x) - 1 = 0 \implies tan(x) = 1 \implies x = \frac{\pi}{4}, \frac{5\pi}{4}

    or
    cos(x) = 0 \implies x = \frac{\pi}{2}, \frac{3\pi}{2}

    -Dan
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  3. #3
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    Thanks so much it was really helpful

    how about this one...
    4Sin(x)tan(x)-3tan(x)+20sin(x)-15
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  4. #4
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by imthatgirl View Post
    Thanks so much it was really helpful

    how about this one...
    4Sin(x)tan(x)-3tan(x)+20sin(x)-15
    umm...i suppose you just want us to factor this.

    tan(x) is common to the first two terms, 5 is common to the last two, so pull those out, we get:

    \tan x (4 \sin x - 3) + 5 (4 \sin x - 3)

    now the 4sin(x) - 3 is common to both terms, so pull that out, we get:

    (4 \sin x - 3)( \tan x + 5)

    and we're done


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