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Math Help - some one check my trig!!

  1. #1
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    some one check my trig!!

    so there's a right triangle
    90 degrees in the bottom left
    30 degrees bottom right
    15 in length
    unknown adjacent
    unknown hypotenuse
    so i did sin(30) = 15/b
    15/sin(30)=30=b
    and did tangent(30)=15/a
    15 * tan(30)= 8.66=a
    is this correct?
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  2. #2
    A Plied Mathematician
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    What is your "15 in length"? What does that correspond to? The length of the side opposite to the 30 degrees? What is b? The hypotenuse? What is a? The side adjacent to the 30 degrees?
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  3. #3
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    Quote Originally Posted by gabriel View Post
    so there's a right triangle
    90 degrees in the bottom left
    30 degrees bottom right
    vertical side is 15 in length
    unknown adjacent to the 30 degree angle
    unknown hypotenuse

    so i did sin(30) = 15/b....

    correct

    15/sin(30)=30=b....correct

    and did tangent(30)=15/a...correct

    15 * tan(30)= 8.66=a... incorrect

    is this correct?
    Using tangent, you have 2 ways to find "a"

    tan30^o=\frac{15}{a}

    \frac{tan30^o}{1}=\frac{15}{a}

    \frac{1}{tan30^o}=\frac{a}{15}

    Now multiply both sides by 15.

    Or....

    tan30^o=\frac{15}{a}

    first multiply both sides by "a"

    atan30^o=\frac{15a}{a}=15

    Finally divide both sides by tan30^o to get "a".

    Notice from your diagram that "a" should certainly be longer than 15 units.
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  4. #4
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    so 15/tan(30) = 25.98 app. 26 is this the final correct answer for a?
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  5. #5
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    Quote Originally Posted by gabriel View Post
    so 15/tan(30) = 25.98 app. 26 is this the final correct answer for a?
    Yes,
    but you need to be "correct" on the technique!
    When you are, you will get very used to having correct answers.
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