Sorry, this is nothing about image, I just don't know how to ask the question properly.

My question is, I am writing a C++ code, and doing a calculation.

```
a=b*cos(c)

```

`b` is varying with time from zero to its amplitude, say `bmax`. (actually, `b=bmax*sin(t)`.)

However, I found when `b` is very small, the result `a` is gradually deviating from my analytic results.

So I am wondering how to keep a very high resolution of the results, to avoid the cut-off of the floating points.