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Math Help - Finding value of x

  1. #1
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    Finding value of x

    What is the value of x if 180 < x < 270. (less than OR equal to 270, greater than OR equal to 180) and sinx = 5cosx.

    Ok, I graphed both of these and searched for point of intersection.. The answer is 4.515. I'm a bit confused. I thought that the limits would put the answer in quadrant 3. Why, then, is the solution positive x?
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  2. #2
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    Re: Finding value of x

    Quote Originally Posted by benny92000 View Post
    What is the value of x if 180 < x < 270. (less than OR equal to 270, greater than OR equal to 180) and sinx = 5cosx.

    Ok, I graphed both of these and searched for point of intersection.. The answer is 4.515. I'm a bit confused. I thought that the limits would put the answer in quadrant 3. Why, then, is the solution positive x?
    \sin{x} = 5\cos{x}

    \frac{\sin{x}}{\cos{x}} = 5

    \tan{x} = 5

    since 180 < x < 270

    x = \arctan(5) + 180

    tangent is positive in quad III

    btw ... your answer is correct, it's in radians
    Last edited by skeeter; August 14th 2011 at 04:02 PM.
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