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  • Perplex
    IB Math AAHL
    /
    Trig equations & identities
    /

    Problem Bank

    [Maximum mark: 17]

    Define the ​Error​ between two functions, ​f(x)​ and ​g(x)​ evaluated at ​n​ is given by​∫−nn​(f(x)−g(x))2dx.

    1. Find the ​Error​ in terms of ​n​ between the functions ​cos(x)​ and ​sin(x).

      [3]

      To earn a crown, get your answer ready before you reveal the options!

    Suppose that we would like to fit a linear model, ​ax+b, to the function ​y=2x2+4x+1​ close to ​x=0.

    1. Show that the error between ​2x2+4x+1​ and ​ax+b​ evaluated at ​n​ is given by ​58​n5+32n3​(a2−8a+20−4b)+2n(1−b)2.

      [5]
    2. Hence, determine the value of ​a​ minimising the ​Error.

      [2]
    3. Similarly, find the value of ​b​ minimising the error in terms of ​n.

      [2]
    4. By considering ​n→0, find the line best approximating the function in the neighborhood of ​x=0.​

      [2]
    5. Verify that this gives the same answer as the tangent line at ​x=0.

      [3]

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