public async Task <double> Calculate(double from, double to, int n, Math.Expression func)
{
var area = 0.0;
var dx = (to - from) / n;
await Task.Run(() =>
{
area += func.CalculateWith(from) / 2;
area += func.CalculateWith(to) / 2;
for (var i = 1; i < n; i++)
{
area += func.CalculateWith(from + dx *i);
}
});
return(dx * area);
}