一道高中数学题lg2+lg5=lg10,lg2.lg5=?

设 lg2 = x ,则 10^x = 2
lg5 = y ,则 10^y = 5
因为：2×5 = 10
即 10^x × 10^y = 10^(x+y) = 10
10^(x+y) = 10 其实就是 (x + y) = 1
两边取对数 (x+y) = Lg10
所以：lg2 + lg5 = x + y = lg10 = 1
Lg2×Lg5 = x×y = Lg[2^(Lg5)] 或者 Lg[5^(Lg2)]