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Logarithms
O-Level A Math
Laws of Logarithms
$$\log_a xy = \log_a x + \log_a y$$
$$\log_a \dfrac{x}{y} = \log_a x - \log_a y$$
$$\log_a x^r = r \log_a x$$
$$\log_a 1 = 0$$
$$\log_a a = 1$$
Change of Base
$$\log_a b = \dfrac{\log_c b}{\log_c a}$$
$$\log_a b = \dfrac{1}{\log_b a}$$
Common special cases: $\log_{10}$ (common log) and $\ln = \log_e$ (natural log)
Formulas for the Singapore O-Level Additional Mathematics syllabus