>>584
y ' = {log[ｘ+√(ｘ^2ｰa^2)] / log(a) } '
= {1 + x/√(x^2-a^2)}/{ x + √(x^2-a^2)} / log(a)
= [{√(x^2-a^2) + x}/√(x^2-a^2)] / [{x + √(x^2-a^2)} * log(a)]
= 1 / {log(a) * √(x^2-a^2)}