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I think I got the period right, but I don’t know the rest. What is the equation?

I think I got the period right, but I don’t know the rest. What is the equation?-example-1
User Luiss
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1 Answer

19 votes
19 votes

Solution

- The general form of a sinusoidal function is:


\begin{gathered} f(x)=A\sin B(x-h)+k \\ where, \\ |A|=\text{ Amplitude} \\ Period(T)=(2\pi)/(|B|) \\ \\ y=k\text{ \lparen The Midline\rparen} \end{gathered}

- First of all, let us find the value of B using the period formula given above.


\begin{gathered} \text{ We are told that the period is 6} \\ \therefore T=(2\pi)/(|B|) \\ \\ 6=(2\pi)/(|B|) \\ \text{ Make \mid B\mid the subject of the formula} \\ \\ \therefore|B|=(2\pi)/(6) \\ \\ |B|=(\pi)/(3) \\ \\ \text{ Thus,} \\ B=\pm(\pi)/(3) \\ \\ \text{ Since there is only the positive }(\pi)/(3)\text{ in the options,} \\ \\ B=(\pi)/(3) \end{gathered}

- Next, we should apply the condition given to us that f(2.5) = 5


\begin{gathered} f(x)=A\sin Bx+H \\ B=(\pi)/(3) \\ \\ f(x)=A\sin(\pi)/(3)x+H \\ \\ f(2.5)=5\text{ implies that }x=2.5,f(x)=5 \\ \\ 5=A\sin(\pi)/(3)(2.5)+H\text{ \lparen Equation 1\rparen} \end{gathered}

- We also know that the Amplitude and Valley are related to the midline as follows:


\begin{gathered} H-MinValue=A \\ MinValue=2 \\ \\ H-2=A \\ \therefore H-A=2\text{ \lparen Equation 2\rparen} \end{gathered}

Solving equations 1 and 2 simultaneously, we have

User Iamarkadyt
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