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    Like how can I use it? what is 'n' in this case?!
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    (Original post by Adorable98)
    Like how can I use it? what is 'n' in this case?!
    Basically means if you want a root of cosine, you substitute any value of n into the equation
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    (Original post by Andy98)
    Basically means if you want a root of cosine, you substitute any value of n into the equation
    Could you please give me an example?
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    (Original post by Adorable98)
    Could you please give me an example?
    If you wanted the second root, you'd do  \frac{((2*2)+1)π}{2}=\frac{3π}  {2}

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    (Original post by Andy98)
    If you wanted the second root, you'd do  \frac{((2*2)+1)π}{2}=\frac{3π}  {2}

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    I see, thank you.
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    (Original post by Adorable98)
    I see, thank you.
    Yeah, should be 5 not 3, my bad

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    (Original post by Andy98)
    Basically means if you want a root of cosine, you substitute any value of n into the equation
    The roots of the cosine curve you drew are the points where it intersects with the X-axis. These turned out to be: -3PI/2, -PI/2, PI/2, 3PI/2
    So the pattern of these roots is: (2n+1)PI/2
    when n=-2: the root is ((2*-2)+1)PI/2= -3PI/2
    when n=-1: the root is ((2*-1)+1)PI/2= -PI/2
    when n=0: the root is ((2*0)+1)PI/2= PI/2
    when n=1: the root is ((2*1)+1)PI/2= 3PI/2
    Since the cosine curve is periodic, it will keep following the same shape forever, and so will keep crossing the X-axis many more times. So it has an infinite number roots (and not just 4), and has to be written in the general form (2n+1)PI/2.
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    Note that n is a whole number, though that's probably obvious
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    (Original post by Adorable98)
    ...
    All that it's saying is that the roots of \cos \theta which are the solutions to the equation \cos \theta = 0 occur at odd multiples of \frac{\pi}{2}. So they could occur at 1 multiple of \frac{\pi}{2} or 3 multiples 3 \cdot \frac{\pi}{2} or 5 multiples, or -3 multiples or -101 multiples etc... as just odd multiples of \frac{\pi}{2}.
 
 
 
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