package main

import (
	"bufio"
	"fmt"
	"os"
)

func main() {
	in := bufio.NewReader(os.Stdin)
	out := bufio.NewWriter(os.Stdout)
	defer out.Flush()

	var t int
	if _, err := fmt.Fscan(in, &t); err != nil {
		return
	}

	for i := 0; i < t; i++ {
		var R, r, k float64
		fmt.Fscan(in, &R, &r, &k)
		num := R * r * (R - r)
		den := R*r + k*k*(R-r)*(R-r)
		fmt.Fprintf(out, "%.15f\n", num/den)
	}
}