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Math Help - trigonometric graph

  1. #1
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    trigonometric graph

    Prof never went over this in class, don't really know what to do..

    Find the first three x-intercepts of the graph of the given function on the positive x-axis.

    f(x) = 1 - 2cos(x+pi/3)

    Any help (explanations, steps) would be great, thanks!

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

    Also... have a problem with this question..

    Use the given information to find the values of the remaining five trigonometric functions.

    cotx = 1/2, pi < x < 3pi/2

    Thanks ><!
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  2. #2
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    Quote Originally Posted by zuuberbat View Post
    Prof never went over this in class, don't really know what to do..

    Find the first three x-intercepts of the graph of the given function on the positive x-axis.

    f(x) = 1 - 2cos(x+pi/3)

    [snip]
    Solve 1 - 2 \cos \left( x +\frac{\pi}{3} \right) = 0 \Rightarrow \cos \left( x + \frac{\pi}{3} \right) = \frac{1}{2} for x > 0.
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  3. #3
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    Quote Originally Posted by zuuberbat View Post
    Prof never went over this in class, don't really know what to do..

    Find the first three x-intercepts of the graph of the given function on the positive x-axis.

    f(x) = 1 - 2cos(x+pi/3)

    Any help (explanations, steps) would be great, thanks!

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

    Also... have a problem with this question..

    Use the given information to find the values of the remaining five trigonometric functions.

    cotx = 1/2, pi < x < 3pi/2

    Thanks ><!
    Obviously tan x = 2.

    Substitute into \sin^2 x + \cos^2 x = 1 \Rightarrow \tan^2 x + 1 = \frac{1}{\cos^2 x} and solve for \cos x (note that \cos x < 0 for \pi < x < \frac{3 \pi}{2})

    Get sin x from cos x etc.
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