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Math Help - A quick explaination

  1. #1
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    A quick explaination

    hi guys,

    I dont know if this is in the right forum because it involves trig stuff. So mod, feel free to move it.

    i was just going through some work on the topic 'area between two curves' and i was given the equations as:

    f(x) = sin x, and g(x) = sin(2x), a = 0 and b = 'pi'

    The solution states that the intersection point could be found as:

    sin x = sin(2x), then x = 'pi' - 2x and hence x = 'pi'/3.

    i was wondering could someone show me how the step by step as to how they derived the intersection point? Because i never did trig before

    Thanks in advance
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  2. #2
    Member Ruun's Avatar
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    Hi

    sin (2x) = 2 sin (x) cos (x) and in the problem sin (2x) = sin (x) . If  x \neq 2\pi k, k \in \mathbb{Z}, then  2 cos (x) = 1 thus  x = \frac {\pi}{3}
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  3. #3
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    Thanks.

    If its not too much trouble could you explain a lil bit further please?
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  4. #4
    Member Ruun's Avatar
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    Quote Originally Posted by Redeemer_Pie View Post
    Thanks.

    If its not too much trouble could you explain a lil bit further please?
    No problem, just translation of the math language:

    We know that sin (2x) = 2 sin (x) cos (x). Your problem states that sin (2x) = sin (x) , so  2 sin (x) cos (x) = sin (x) . Now, if  sin (x) \neq 0 we can divide by it and  2 cos (x)  = 1 =>  x = \frac{1}{3} \pi
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  5. #5
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    Thanks mate
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