Average Error: 0.5 → 0.4
Time: 7.8s
Precision: 64
\[\sqrt{x - 1} \cdot \sqrt{x}\]
↓
\[x - \left(0.5 + \frac{0.125}{x}\right)\]
\sqrt{x - 1} \cdot \sqrt{x}
↓
x - \left(0.5 + \frac{0.125}{x}\right)
double f(double x) {
        double r9375 = x;
        double r9376 = 1.0;
        double r9377 = r9375 - r9376;
        double r9378 = sqrt(r9377);
        double r9379 = sqrt(r9375);
        double r9380 = r9378 * r9379;
        return r9380;
}
↓
double f(double x) {
        double r9381 = x;
        double r9382 = 0.5;
        double r9383 = 0.125;
        double r9384 = r9383 / r9381;
        double r9385 = r9382 + r9384;
        double r9386 = r9381 - r9385;
        return r9386;
}

Error

Bits error versus x

Try it out

Your Program's Arguments

Results

Enter valid numbers for all inputs

Derivation

  1. Initial program 0.5

    \[\sqrt{x - 1} \cdot \sqrt{x}\]

  2. Taylor expanded around inf 0.4

    \[\leadsto \color{blue}{x - \left(0.5 + 0.125 \cdot \frac{1}{x}\right)}\]

  3. Simplified0.4

    \[\leadsto \color{blue}{x - \left(0.5 + \frac{0.125}{x}\right)}\]

  4. Final simplification0.4

    \[\leadsto x - \left(0.5 + \frac{0.125}{x}\right)\]

Reproduce

herbie shell --seed 2019325 
(FPCore (x)
  :name "sqrt times"
  :precision binary64
  (* (sqrt (- x 1)) (sqrt x)))