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    Hey, I have been going through past papers and answering all questions on certain topics as a part of my C3/C4 revision. However, I am on my last Trigonometry question (yay!) but I can't seem to do part 8(c)

    the question paper is on this link:
    http://www.examsolutions.net/a-level...y/paper.php#Q5

    I got 8(a) correct and also part (b). However, I can only get one of the solutions on part (c) [the solution I have is 5pi/12]. I am unsure how they arrived at the second sollution [11pi/12] and I am unsure how they arrived at the formula 2pi-feta=feta+pi/6

    Any help would be appreciated; thank you!!!
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    (Original post by jessica_anne_clu)
    Hey, I have been going through past papers and answering all questions on certain topics as a part of my C3/C4 revision. However, I am on my last Trigonometry question (yay!) but I can't seem to do part 8(c)

    the question paper is on this link:
    http://www.examsolutions.net/a-level...y/paper.php#Q5

    I got 8(a) correct and also part (b). However, I can only get one of the solutions on part (c) [the solution I have is 5pi/12]. I am unsure how they arrived at the second sollution [11pi/12] and I am unsure how they arrived at the formula 2pi-feta=feta+pi/6

    Any help would be appreciated; thank you!!!
    In part (b) you found an expression for tan(\theta + \pi/6)

    In part(c), if you divide both sides of the equation by (\sqrt{3} - tan \theta) then the LHS is the expression you worked with in part (b).

    This means that you now need to solve the equation:
    tan(\pi - \theta) = tan(\theta + \pi/6)

    One solution to this is obviously going to be when
    \pi - \theta = \theta + \pi/6

    which you can rearrange and solve, and check that the value for theta is in the required range.

    However, remember that tan is periodic and when you solve tan A = tan B there will be other solutions - you should have covered this as part of your bookwork. All you have to do is check which solutions are going to give you angles in the correct range
 
 
 
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