Pattern Recognition In Exercises $69$ and $70,$ use a graphing utility to compare the graph of $f$ with the given graph. Try to improve the approximation by adding a term to $f(x).$ Use a graphing utility to verify that your new approximation is better than the original. Can you find other terms to add to make the approximation even better? What is the pattern? $($In Exercise $69,$ sine terms can be used to improve the approximation and in Exercise $70,$ cosine terms can be used.$)$

$69.f(x)=\frac{4}{}(sinx+\frac{1}{3}sin3x)$