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Math Help - Trig - Quadratic Function Help

  1. #1
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    Trig - Quadratic Function Help

    Hi, first time poster, long time reader, Here I am as im stuck on some questions for a quiz. Ive looked in notes and books and still cant figure them out...anyway, here they are. Can anyone give me a clue, how I do it...or even the answers...aha..preferably both!

    What angles (in radians) in have a cosine of

    1 /2

    I know the answer to this is pi/3.

    The next question is:

    In which quadrant is the other angle whose cosine is

    1 / 2

    And I know it is Quad 4...

    Now...what I dont know is Part C) which is....

    Angle not in 1st quadrant:

    So how do I find out the angle not in the first quadrant (which is worked out to be Quad 4)?

    ...............


    (I am also stuck on the same question where the angle is pi/6 and need the angle in the 3rd quadrant)
    Last edited by Maccabhoy; April 22nd 2009 at 12:41 PM.
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  2. #2
    A riddle wrapped in an enigma
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    Quote Originally Posted by Maccabhoy View Post
    Hi, im stuck on some questions for a quiz. Ive looked in notes and books and still cant figure them out...anyway, here they are. Can anyone give me a clue, how I do it...or even the answers...aha..preferably both!

    What angles (in radians) in have a cosine of

    1 /2

    I know the answer to this is pi/3.

    The next question is:

    In which quadrant is the other angle whose cosine is

    1 / 2

    And I know it is Quad 4...

    Now...what I dont know is Part C) which is....

    Angle not in 1st quadrant:

    So how do I find out the angle not in the first quadrant?

    ...............


    (I am also stuck on the same question where the angle is pi/6 and need the angle in the 3rd quadrant)
    Hi Maccabhoy,

    In all that wording, I'm not sure what you can't find. Sounds like you need a picture of the unit circle. Look here! Print yourself a copy and keep it handy.

    As you can see from the table \cos \frac{\pi}{6}=\frac{1}{2} which is in QI.

    And \cos \frac{5\pi}{3}=\frac{1}{2} in QIV.

    Does that answer your question?
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  3. #3
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    Quote Originally Posted by masters View Post
    Hi Maccabhoy,

    In all that wording, I'm not sure what you can't find. Sounds like you need a picture of the unit circle. Look here! Print yourself a copy and keep it handy.

    As you can see from the table \cos \frac{\pi}{6}=\frac{1}{2} which is in QI.

    And \cos \frac{5\pi}{3}=\frac{1}{2} in QIV.

    Does that answer your question?
    Hey Masters, thanks for the reply. Not sure you have answered the question.... But that's my fault, as I think my explanation isnt the best. I'll try to copy and paste the question direct (As you will see, I got the answers for 8.1 and 8.2 correct and just need 8.3)

    ----------------------

    What angles (in radians) in have a cosine of
    1/2?
    Your angles should be given exactly. Recall that π is entered as: pi or Pi.
    8.1 (1 mark)


    Angle in 1st quadrant:

    Your last answer was:
    1/3 π

    Your answer is correct.
    The mark for your last attempt was 1.00


    8.2 (1 mark)
    In which quadrant is the other angle whose cosine is 1/2 ?

    Answer 2 for 2nd quadrant, 3 for 3rd quadrant, or 4 for 4th quadrant.

    Note: penalties for wrong answers are higher than usual. Don't just guess!
    Answer:

    Your last answer was:
    4

    Your answer is correct.
    The mark for your last attempt was 1.00


    8.3 (1 mark) Angle not in 1st quadrant:
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  4. #4
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    And here is the other question, where again ive answered 9.1 and 9.2 correctly but can't figure out 9.3

    Question 9 (3 marks) Top 1 2 3 4 5 6 7 8 9 10 Bottom Validate Mark Focus Help What are the angles (in radians) whose tangent is

    1 /√3
    ? Your angles should be given exactly. Recall that π is entered as: pi or Pi.
    9.1 (1 mark)

    Angle in 1st quadrant:

    Your last answer was:
    1/6 π

    Your answer is correct.
    The mark for your last attempt was 1.00


    9.2 (1 mark)
    In which quadrant is the other angle whose tangent is

    1 /√3
    ? Answer 2 for 2nd quadrant, 3 for 3rd quadrant, or 4 for 4th quadrant.

    Note: penalties for wrong answers are higher than usual. Don't just guess!
    Answer:

    Your last answer was:
    3

    Your answer is correct.
    The mark for your last attempt was 1.00


    9.3 (1 mark)

    Angle not in 1st quadrant:
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  5. #5
    A riddle wrapped in an enigma
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    Quote Originally Posted by Maccabhoy View Post
    Hey Masters, thanks for the reply. Not sure you have answered the question.... But that's my fault, as I think my explanation isnt the best. I'll try to copy and paste the question direct (As you will see, I got the answers for 8.1 and 8.2 correct and just need 8.3)

    ----------------------

    What angles (in radians) in have a cosine of
    1/2?
    Your angles should be given exactly. Recall that π is entered as: pi or Pi.
    8.1 (1 mark)


    Angle in 1st quadrant:

    Your last answer was:
    1/3 π

    Your answer is correct.
    The mark for your last attempt was 1.00


    8.2 (1 mark)
    In which quadrant is the other angle whose cosine is 1/2 ?

    Answer 2 for 2nd quadrant, 3 for 3rd quadrant, or 4 for 4th quadrant.

    Note: penalties for wrong answers are higher than usual. Don't just guess!
    Answer:

    Your last answer was:
    4

    Your answer is correct.
    The mark for your last attempt was 1.00


    8.3 (1 mark) Angle not in 1st quadrant:
    Looks to me like they're asking for the angle in quadrant IV whose cosine is also 1/2 which would be \frac{5\pi}{3}. This angle is not in the 1st quadrant and seems to answer the question. Am I missing something?
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  6. #6
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    Quote Originally Posted by masters View Post
    Looks to me like they're asking for the angle in quadrant IV whose cosine is also 1/2 which would be \frac{5\pi}{3}. This angle is not in the 1st quadrant and seems to answer the question. Am I missing something?
    No that is right! Thanks! I had typed that previously but got it wrong as I wasnt using the correst syntax for this online program!!
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