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    Question 20 in the mixed exercise of trig identities...

    The diagram shows part of a curve with equation f(x) = 1+2sin(px+q) p and q being positive constants and q < 90.

    Give than the coordinates of A and C are (0,2) and (45,0) respectively:

    Calculate value of q - DONE

    show that p = 4

    Not sure how to do this one.. I get so far as...

    sin(45p +30) = -30

    But when I looked up the answer it should be

    sin (45p+30) = 210

    I now p is supposed to be postive - but just not sure where the 210 comes from because i get -30.....

    Thanks for any help you can give :-)

    This is the link to the question if you need the full thing...

    https://doc-14-5o-docs.googleusercon...Th1MnhZTHM4VTg
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    Remember sin has two solutions (by this I mean the other solutions are just +/- 360 degrees). Say one is x. The other one is then 180-x. In your case 180--30=210 (degrees)
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    (Original post by christinajane)
    Question 20 in the mixed exercise of trig identities...


    This is the link to the question if you need the full thing...

    https://doc-14-5o-docs.googleusercon...Th1MnhZTHM4VTg
    The link does not work
    Better fix it !!
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    (Original post by christinajane)
    Question 20 in the mixed exercise of trig identities...

    The diagram shows part of a curve with equation f(x) = 1+2sin(px+q) p and q being positive constants and q < 90.

    Give than the coordinates of A and C are (0,2) and (45,0) respectively:

    Calculate value of q - DONE

    show that p = 4

    Not sure how to do this one.. I get so far as...

    sin(45p +30) = -30

    But when I looked up the answer it should be

    sin (45p+30) = 210

    I now p is supposed to be postive - but just not sure where the 210 comes from because i get -30.....

    Thanks for any help you can give :-)

    This is the link to the question if you need the full thing...

    https://doc-14-5o-docs.googleusercon...Th1MnhZTHM4VTg
    If you draw the sin graph for -180<x<180, you can see that there are 4 different values x could take when y=-0.5 with the lowest, positive value being 210. Therefore that is the value you take and put in the equation
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    (Original post by NNB_Herath)
    The link does not work
    Better fix it !!
    oops sorry!

    https://0e90d90be05fe2865012661b731d...apter%2010.pdf
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    (Original post by Math12345)
    Remember sin has two solutions (by this I mean the other solutions are just +/- 360 degrees). Say one is x. The other one is then 180-x. In your case 180--30=210 (degrees)
    Ahhh ok that makes sense! thanks For that.
 
 
 
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