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Math Help - another intro to circular functions question.

  1. #1
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    another intro to circular functions question.

    find the value of theta to the nearest second.

    - sin theta= -0.4545 and theta is in the 4th quadrant


    -sec theta= 2/3 and theta is in the 1st quadrant
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  2. #2
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    Quote Originally Posted by Dave19 View Post
    find the value of theta to the nearest second.

    - sin theta= -0.4545 and theta is in the 4th quadrant


    -sec theta= 2/3 and theta is in the 1st quadrant
    Here, a calculator must be used.

    sin(theta) = -0.4545
    So, theta = arcsin(-0.4545)
    By calculator, theta = -27 degees.
    That is if theta were meausured counterclockwise as usual.

    The negative then means theta should be measured clockwise. Then theta will fall in the 4th quadrant.
    Theta then = 360 -27 = 333 degrees. ....in the usual, counterclockwise, measuring.

    ----------------
    sec(theta) = 2/3

    In a calculator, there are no sec or arcsec functions. Only cos or arccos functions.
    So convert the sec into cos first so that you can use the calculator.

    sec = 1/cos
    So, cos = 1/sec

    cos(theta) = 1/(2/3) = 3/2 = 1.5
    Cannot be.
    The maximum value of cos is only 1.0

    The question is wrong.
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