IB SL Find the least positive value of x for which cos(x/2+pi/3) =1/sqrt(2)

Posted on March 9, 2023 by Sumant Sumant

About Sumant Sumant

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3 Responses to IB SL Find the least positive value of x for which cos(x/2+pi/3) =1/sqrt(2)

  1. disho74 says:
    September 26, 2023 at 3:06 am

    I can follow until the result is equal to -π/6, but I don’t get 7π/4
    I would appreciate it if you explained it a little bit more

    Reply
    • Sumant Sumant says:
      September 26, 2023 at 3:23 am

      I just rewrote the solution. Let me know if it makes sense. cos(x) achieves \dfrac{1}{\sqrt{2}} at two different angles 45 degree and 315 degree in its domain. We first try 45 degree or \dfrac{\pi}{4} it gives negative value of x so we reject it and then we try 315 degree \dfrac{7\pi}{4} and this time it gives positive value of x. So it must be the first time x achieves a positive value. Therefore it must be the least positive value of x. Hope that helps.

      Reply
  2. disho74 says:
    September 26, 2023 at 3:32 am

    Much appreciated, it is clear now, thank you

    Reply

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