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Math Help - How to solve trig equations - is it ok to take values off graph

  1. #1
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    How to solve trig equations - is it ok to take values off graph

    Hello

    I am studying A level maths A2 in UK. So level is pre-University maths.

    I have for example, this equation to solve for 0 <= x <= 360.

    cosec x = sec x.

    I am solving like this:

    \frac{1}{sin x} = \frac{1}{cos x}

    sin x = cos x

    x = 45 and 225 degrees.

    Then looking on a graph of sin and cos x to see where they intersect. Is that the way to do it? Or is there a more rigorous method? Is there an algebraic method?

    Angus
    Last edited by angypangy; December 7th 2011 at 05:19 AM.
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  2. #2
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    Re: How to solve trig equations - is it ok to take values off graph

    \sin x = \cos x \Rightarrow \tan x= 1 \Rightarrow x_1 = \frac{\pi}{4} , x_2=\frac{5\pi}{4}
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  3. #3
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    Re: How to solve trig equations - is it ok to take values off graph

    for completeness you could also check that there are no solutions where sinx=cosx=0 (this is in fact the case)
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