Nei WADA also calculated Fermat's Principle, that is to say, (f(x + e/2) - f(x - e/2))/e, and delivered the method in which it was expressed as e 0.
同じ脈絡で、和田寧はフェルマーの方法、すなわち(f(x+e/2)-f(x-e/2))/eを計算し、e0とする方法を発表している。