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Math Help - trig exact values

  1. #1
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    trig exact values

    Please help me with finding trig exact values. I have always relied on my calculator to give me answers for these problems but now my prof. makes us use a calculator that cant convert decimals to fractions. I know how to do it with easy values when using the special triangles but what do I do when you have something like:

    Find the exact value for cos(4/5)
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  2. #2
    Grand Panjandrum
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    Re: trig exact values

    Quote Originally Posted by jmanna98 View Post
    Please help me with finding trig exact values. I have always relied on my calculator to give me answers for these problems but now my prof. makes us use a calculator that cant convert decimals to fractions. I know how to do it with easy values when using the special triangles but what do I do when you have something like:

    Find the exact value for cos(4/5)
    Sorry but that makes no sense, your calculator can tell you what cos(0.8) is can't it?

    It will also let you enter cos(4/5) directly

    CB
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  3. #3
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    Re: trig exact values

    sorry the question is arccos(4/5), therefore cos(theta)=4/5. How would I find the angle?
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  4. #4
    Grand Panjandrum
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    Re: trig exact values

    Quote Originally Posted by jmanna98 View Post
    sorry the question is arccos(4/5), therefore cos(theta)=4/5. How would I find the angle?
    Think 3,4,5 triangle, and there is no "exact" value of arccos(4/5).

    CB
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