Question

よっちゃん

57.9=20log10(2.22/V)
の解き方、答えを教えてください。

対数

Answer 1

高橋

20log10(2.22/V) = 57.9
log10(2.22/V) = 2.895 = 2+0.895
2 = log10(100)
常用対数表より、log10(7.85) = 0.8949
よって、log10(2.22/V) = log10(100)+log10(7.85) = log10(100×7.85) = log10(785)
2.22/V = 785
V = 2.22/785 = 0.00283