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Homework Help: Tangent Line to f(x) Without Specified Point

  1. Aug 10, 2012 #1
    1. The problem statement, all variables and given/known data

    Hello again.

    The question asks me to find an equation of the tangent to the graph:

    [tex]f(x)= - sin^2 x + 1/2, x \epsilon [0, \frac{\pi}{2}[/tex]

    which makes an angle of 135° with the x-axis (measure anti-clockwise from the positive x-axis). Assume that the scales along the x- and y- axis are the same.

    I just don't know how to find the point.

    2. Relevant equations

    3. The attempt at a solution

    What I did was took the 135° value from the unit circle, which I think is:
    [tex]\frax{3\pi}{4} [/tex]
    and worked with that as my x-coordinate.

    The problem is that the question states that x ε [0, ∏/2], which means that 3∏/4 can't be x.

    The only other value I can think of getting is:
    √2/2 from sin(2∏ - 3∏/4).

    What am I overlooking?
  2. jcsd
  3. Aug 10, 2012 #2

    Simon Bridge

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    Science Advisor
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