Question

Diketahui log 2 = 0,3010, lg 3 = 0,4771 dan log 7 = 0,8451. tentukan:
a. log 18
b. log 21
c. log 10,5
d. log 1/7

Answer 1

A. log 18 = log(2.3.3)=log2+log3+log3=0.3010+0.4771+0,4771=itung sendiri
yg lain coba sendiri aja 

Answer 2

a) log 18 = log(3² x 2) 
= log 3² + log 2 
= 2 * log 3 + log 2 = 2(0,4771) + (0,3010) 
= 1.2552 

b. log 21 = log(7 x 3) 
= log 7 + log 3 = 0,8451 + 0,4771 
= 1.3222 

c. log 10,5 = log(105/10) 
= log(3 x 5 x 7) / 10) 
= log 3 + log 5 + log 7 - log 10 
= 0,3010 + 0,4771 + 0,8451 - 1 
= 0.6232 

d. log (1/7) = log 7⁻¹ = -log 7 
= -0,8451