How do I do this coding for this C++ problem

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C++

mathematics

Equation : -0.87 sin (4x) - 0.56 log (4x) + 1.32 ln (5x)
Range of x : 8<= x <18
Step of x : 0.100

1. Generate value of f(x)?
2. Convert to rad?
3. Perform magnitude scaling on f(x) such that the scaling ranges a and b are given by user, where 𝑎<𝑏 and 𝑎>0. The scaled output 𝑓𝑠𝑐𝑎𝑙𝑒𝑑 can be found from: 𝑓𝑠𝑐𝑎𝑙𝑒𝑑=[(b−a)(𝑓(𝑥)−min(𝑓(𝑥)))]/[max(𝑓(𝑥))−min⁡(𝑓(𝑥))+𝑎]
4. Find standard deviation of 𝑓𝑠𝑐𝑎𝑙𝑒𝑑 for 5 evenly divided quantiles of 𝑓𝑠𝑐𝑎𝑙𝑒𝑑 and find the frequency of occurrence within each quantile.
3. Find variances of 𝑓𝑠𝑐𝑎𝑙𝑒𝑑 for 5 evenly divided quantiles of 𝑓𝑠𝑐𝑎𝑙𝑒𝑑 and find the frequency of occurrence within each quantile.
4. Remove values of 𝑓𝑠𝑐𝑎𝑙𝑒𝑑 which is less than P, where P will be entered by user and 𝑎≤𝑃≤𝑏. Then find the means of 𝑓𝑠𝑐𝑎𝑙𝑒𝑑⁡for each 5 evenly divided quantiles of the new data

What I have tried:

I dont know to conert it to rad and fx. then I dont quite understand what is the fscaled