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  1. #1
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    Need help here

    Trigonometric formulas,identites and equation


    solve each equation for nonnegative angles less than 360deg or 2 pi



    1)2cos x=3
    2)sinxcosx=0
    3)sin theta - cos theta=0
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by cheesepie
    1)2cos x=3
    Not possible if we are restricted to real angles as:

    <br />
2 \cos(x)=3 means that \cos(x)=3/2 >1 <br />

    RonL
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  3. #3
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    Quote Originally Posted by cheesepie
    Trigonometric formulas,identites and equation

    solve each equation for nonnegative angles less than 360deg or 2 pi

    1)2cos x=3
    2)sinxcosx=0
    3)sin theta - cos theta=0
    Hello,

    to 1) There isn't any real solution because in your problem cos(x) = 3/2.
    But: -1 \leq \cos(x) \leq 1

    to 2) A product of two factors is zero if one (or both) factor is zero:
    \sin(x) \cdot \cos(x)=0 \Longleftrightarrow \sin(x)=0\ \vee \ \cos(x)=0
    So x \in \{0^\circ, 180^\circ,360^\circ, 90^\circ, 270^\circ \}

    to 3)Add cos(x) to both sides of your equation and divide then by cos(x). You'll get the equation:
    \sin(x) = \cos(x) \Longleftrightarrow \tan(x)=1.
    So x \in \{45^\circ, 225^\circ \}

    Greetings

    EB
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  4. #4
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    thanx alot for ur reply ..
    Last edited by cheesepie; April 26th 2006 at 12:45 AM.
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