cos(a)×cos(b) = 1
2(cos(a+b) + cos(a−b))
. . .
. . .
. . .
log(10) = 1 log(100) = 2,log(1000) = 3
1,5 = 1
2×3 = 1
2log(1000) = log(10001/2)= log(√1000)
√1000 '31,62277 log(31,62277) =
1,5
φ
x y φ(xy) = φ(x) + φ(y)
φ(1) = 0
x6= 0 φ(1
x) = −φ(x)
x, y y 6= 0 φ(x
y) = φ(x)−φ(y)
x n ∈Zφ(xn) = nφ(x)
x φ(√x) = 1
2φ(x)
φ φ0(x) = k
xk∈R
ln R∗
+R
(∀x, y ∈R∗
+,ln (xy) = ln (x) + ln (y)
∀x∈R∗
+,ln0(x) = 1
x
1
/
2
100%
