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To fit a sinusoidal function to a set of points that are not symmetrical, follow these steps:

1. Plot the data points on a graph.

2. Determine the general shape of the curve. Is it concave up or down?

3. Use the general form of a sinusoidal function f(x) = a*sin(bx + c) + d to fit the curve. Here, a is the amplitude, b is the frequency, c is the phase shift, and d is the vertical shift.

4. Estimate the amplitude by finding the difference between the maximum and minimum values of the curve.

5. To estimate the frequency, count the number of cycles in the graph, and divide by the range of the x-values.

6. The phase shift is found by determining the horizontal shift needed for the curve to reach its maximum or minimum.

7. Finally, estimate the vertical shift by finding the average of the maximum and minimum values of the data points.

8. Once all the parameters are estimated, use these values to construct the sinusoidal function that best fits the data.