2 log 3 =a dan 2 log 5= b maka nilai 5 log 180

5 log 180 = 2 log 180 / 2 log 5
= 2 log 5.36 / b
= 2 log 5 + 2 log 36 / b
= b + 2 log 6^2 / b
= b + 2 (2 log 2.3) / b
= b + 2 (2 log 2 + 2 log 3) / b
= b + 2 (1 + a) / b
= b + 2 + 2a / b