Exponential Functions: (lesson 1 of 3)
Exponential Functions - Introductions
If a>0 and a=1, then the exponential function with base a is given by f(x)=ax.
Natural Exponential Functions
1. The irrational number e=x→∞lim(1+n1)n≈2.71828⋅⋅⋅ or
e=x→0lim(1+x)x1.
2. For each real x, x→∞lim(1+nx)n=ex.
3. f(x)=ex is a natural exponential function.
Derivatives of Exponential Functions
1. dxd[ex]=ex
2. dxd[ef(x)]=ef(x)⋅f′(x).
The hyperbolic cosine and sine functions
The hyperbolic cosine function is defined as
cosh(x)=2exp(x)+exp(−x), −∞<x<∞,
while the hyperbolic sine function is defined as
sin(x)=2exp(x)−exp(−x), −∞<x<∞.
Properties of hyperbolic cosine and sine functions
1. (sinh(x))′=cosh(x) , (cosh(x))′=sinh(x).
2. cosh(x)>sinh(x).
3. cosh2(x)−sinh2(x)=1