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    I'm really struggling to rearrange trig equations. How would I prove the following:

    (4cos2x)/(1+ cos2x) = 4-2sec^2x.

    I get the 2sec^2x using 1/cosx= secx but I don't know which step I'm getting wrong.

    Also, functions, there is one question which I don't understand at all. If f(x) is root(mx + 7) -4, explain how it can be deduced that neither this function or its inverse meet the line y=x, and determine the set of possible values of m. Having worked through the answer with the mark scheme, I don't understand why f(x) is equated to x, to work out the quadratic equation which gets m.

    Not sure how much of that makes sense, but any help would be great
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    Not sure on first part but second is simply this

    You want to find out if f(x) hits the line y = x, therefore for this to be the case f(x) = x at the point where they meet. This is why the markscheme sets f(x) = x to work out the equation!
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    (Original post by spread_logic_not_hate)
    Not sure on first part but second is simply this

    You want to find out if f(x) hits the line y = x, therefore for this to be the case f(x) = x at the point where they meet. This is why the markscheme sets f(x) = x to work out the equation!
    Thank you I worked out the trig bit in the end, just made a mistake with my rearranging.
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    (Original post by definite_maybe)
    Thank you I worked out the trig bit in the end, just made a mistake with my rearranging.
    could you explain how you did the trig question? I can't seem to do it!
 
 
 
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