What is Exponential: Definition and 1000 Discussions
In mathematics, the exponential function is the function
f
(
x
)
=
e
x
,
{\displaystyle f(x)=e^{x},}
where e = 2.71828... is Euler's constant.
More generally, an exponential function is a function of the form
f
(
x
)
=
a
b
x
,
{\displaystyle f(x)=ab^{x},}
where b is a positive real number, and the argument x occurs as an exponent. For real numbers c and d, a function of the form
f
(
x
)
=
a
b
c
x
+
d
{\displaystyle f(x)=ab^{cx+d}}
is also an exponential function, since it can be rewritten as
a
b
c
x
+
d
=
(
a
b
d
)
(
b
c
)
x
.
{\displaystyle ab^{cx+d}=\left(ab^{d}\right)\left(b^{c}\right)^{x}.}
The exponential function
f
(
x
)
=
e
x
{\displaystyle f(x)=e^{x}}
is sometimes called the natural exponential function for distinguishing it from the other exponential functions. The study of any exponential function can easily be reduced to that of the natural exponential function, since
a
b
x
=
a
e
x
ln
b
{\displaystyle ab^{x}=ae^{x\ln b}}
As functions of a real variable, exponential functions are uniquely characterized by the fact that the growth rate of such a function (that is, its derivative) is directly proportional to the value of the function. The constant of proportionality of this relationship is the natural logarithm of the base b:
d
d
x
b
x
=
b
x
log
e
b
.
{\displaystyle {\frac {d}{dx}}b^{x}=b^{x}\log _{e}b.}
For b > 1, the function
b
x
{\displaystyle b^{x}}
is increasing (as depicted for b = e and b = 2), because
log
e
b
>
0
{\displaystyle \log _{e}b>0}
makes the derivative always positive; while for b < 1, the function is decreasing (as depicted for b = 1/2); and for b = 1 the function is constant.
The constant e = 2.71828... is the unique base for which the constant of proportionality is 1, so that the function is its own derivative:
This function, also denoted as exp x, is called the "natural exponential function", or simply "the exponential function". Since any exponential function can be written in terms of the natural exponential as
b
x
=
e
x
log
e
b
{\displaystyle b^{x}=e^{x\log _{e}b}}
, it is computationally and conceptually convenient to reduce the study of exponential functions to this particular one. The natural exponential is hence denoted by
The former notation is commonly used for simpler exponents, while the latter is preferred when the exponent is a complicated expression. The graph of
y
=
e
x
{\displaystyle y=e^{x}}
is upward-sloping, and increases faster as x increases. The graph always lies above the x-axis, but becomes arbitrarily close to it for large negative x; thus, the x-axis is a horizontal asymptote. The equation
d
d
x
e
x
=
e
x
{\displaystyle {\tfrac {d}{dx}}e^{x}=e^{x}}
means that the slope of the tangent to the graph at each point is equal to its y-coordinate at that point. Its inverse function is the natural logarithm, denoted
log
,
{\displaystyle \log ,}
ln
,
{\displaystyle \ln ,}
or
log
e
;
{\displaystyle \log _{e};}
because of this, some old texts refer to the exponential function as the antilogarithm.
The exponential function satisfies the fundamental multiplicative identity (which can be extended to complex-valued exponents as well):
It can be shown that every continuous, nonzero solution of the functional equation
f
(
x
+
y
)
=
f
(
x
)
f
(
y
)
{\displaystyle f(x+y)=f(x)f(y)}
is an exponential function,
f
:
R
→
R
,
x
↦
b
x
,
{\displaystyle f:\mathbb {R} \to \mathbb {R} ,\ x\mapsto b^{x},}
with
b
≠
0.
{\displaystyle b\neq 0.}
The multiplicative identity, along with the definition
e
=
e
1
{\displaystyle e=e^{1}}
, shows that
e
n
=
e
×
⋯
×
e
⏟
n
factors
{\displaystyle e^{n}=\underbrace {e\times \cdots \times e} _{n{\text{ factors}}}}
for positive integers n, relating the exponential function to the elementary notion of exponentiation.
The argument of the exponential function can be any real or complex number, or even an entirely different kind of mathematical object (e.g., matrix).
The ubiquitous occurrence of the exponential function in pure and applied mathematics has led mathematician W. Rudin to opine that the exponential function is "the most important function in mathematics". In applied settings, exponential functions model a relationship in which a constant change in the independent variable gives the same proportional change (i.e., percentage increase or decrease) in the dependent variable. This occurs widely in the natural and social sciences, as in a self-reproducing population, a fund accruing compound interest, or a growing body of manufacturing expertise. Thus, the exponential function also appears in a variety of contexts within physics, chemistry, engineering, mathematical biology, and economics.
Doing some self prep for Diff EQ starting next week.
Determine the decay rate of C14 which has a 1/2 life of 5230. Using e^kt as a function,
I solve using k5230=ln.5 which gives the obvious answer of negative what I want. How do I know to use the reciprocal (ln2) other than to "just know" I...
Homework Statement
The circuit in the diagram utilizes three identical diodes
having I_S = 10−16 A. Find the value of the current I required
to obtain an output voltage V_o = 2.4 V.
If a current of 1 mA is drawn away from the output terminal by a load, what is
the change in output...
Hello,
I've been looking at the derivation of the exponential function, here
http://www.statlect.com/ucdexp1.htm
amongst other places, but I don't get how, why or what the o(delta t) really does. How does it help?
It's really confusing me, and all the literature I've looked at just...
Homework Statement
Consider the inner product
$$\frac{1}{2\pi}\int_0^{2\pi} \left(\frac{3}{5 - 4\cos(x)}\right) e^{-ikx} dx, \quad k \in \mathbb{Z}, \quad x \in \mathbb{R}.$$
Homework Equations
Is there a method to solve this without using the residue theorem, e.g. integration by parts...
Homework Statement
Prove that y(x,t)=De^{-(Bx-Ct)^{2}} obeys the wave equation
Homework Equations
The wave equation:
\frac{d^{2}y(x,t)}{dx^{2}}=\frac{1}{v^{2}}\frac{d^{2}y(x,t)}{dt^{2}}
The Attempt at a Solution
1: y(x,t)=De^{-u^{2}}; \frac{du}{dx}=B; \frac{du}{dt}=-C
2...
hi
I want to solve inflation problem for exponential potential.
v(\phi) = v_0 exp(-\alpha \phi)
(it's known as barrow or pawer law inflation )
we have 2 main equations:
H^2 = 8π G / 3 (1/2 (\dot{\phi})^2 + v(\phi))
\ddot{\phi} + 3H \dot{\phi} + v(\phi)'=0
I must solve this 2 equ...
How do I compute the commutator [a,e^{-iHt}], knowing that [H,a]=-Ea?
I tried by Taylor expanding the exponential, but I get -iEta to first order, which seems wrong.
Hi all, I'd just like to clear up something that's often confused me.
In classes (particularly classical waves/QM) we've often seen the lecturer switch from describing a wave as (most commonly) Acos(kx-{\omega}t) to e^{i(kx-{\omega}t)}
but doesn't the exponential representation include an...
I have to prove the inverse of the matrix e^A. we haven't studied exponential matrices in uni but he gave us the definition of it with the series e^A= I+A+A^2 ... A^k where A^k=0, even for numbers greater than k.
I have tried to think of a way to prove it, but neither my classmates or I found...
We have a matrix with dimension NxN.For some m belongs to N,m0 we have A^m0=0.We consider the exponential matrix e^A=I+A+A^2/(2!)+A^2/(3!)+A^m/(m!).Find the inverse matrix of e^A.
I tried to write the e^A=e^A(m0)+A^m/(m!) or (e^A)^(-1)=(...
Dear All,
I would like to do an exponential function least-squares fitting, but having two or more exponents. For example the function looks like this:
y (x) = A \exp (-x/a) + B \exp (-x/b)
where A, a, B and b are the least-squares fitted parameters. My question is how to obtain the...
OK, I'm new to multi-variable calculus and I got this question in my exercises that asks me to integrate e^{-2(x+y)} over a diamond that is centered around the origin:
\int\int_D e^{-2x-2y} dA
where D=\{ (x,y): |x|+|y| \leq 1 \}
I know that the region I'm integrating over is symmetric...
Homework Statement
State whether (e^4-x) + 2 is an exponential growth function or an exponential decay function. Explain why.
Homework Equations
I want to use the formula f(x) = ae^kx where a>0, and k<0.
The Attempt at a Solution
I know it is an exponential decay formula...
Homework Statement
(2^x - 2^-x)/3=4
Homework Equations
Using log or exponential rules
The Attempt at a Solution
First multiply both sides by 3 so 2^x-2^-x=12
I thought I could take the log of both sides then condense the log, but that is not right.
I also attempted to...
$$f(y) = \begin{cases} \int_0^y\frac1\beta e^{\frac {-t}\beta}dt = -e^{\frac {-y}\beta}+1 & \text{for } 0 ≤ y < ∞,\\ 0& \text{for } elsewhere\end{cases}$$
P(Y>3) = 1 - P(Y ≤ 3) = 1 - (-e^{-3/beta}+1) = .1353
When I take log to both sides, I get 3.453.
When I take ln to both sides, I get...
The amount of time to finish a operation has an exponential distribution with mean 2 hours
Find the probability that the time to finish the operation is greater than 2 hours.
My thinking is to integrate the exponential probability function. After integrating it, I got -e^{-y/2} + 1 , 0 ≤ y...
Is there a good example of a probability distribution where the support set does not depend on the parameters and is still not a member of the exponential family?
Hi,
Is it possible to find a value of ##n## for the following expression other than by exhaustive search?
$$e^{\frac{2n\pi i p}{q}}=e^{-\pi i p/q},\quad n=1,2,\cdots, q-1, \quad (p,q)\in \mathbb{N}\backslash 0$$
I can write a short program to search for the value of n, but that would...
Hello everyone,
I was solving this problem:
Justify that ln6= ln2+ln3
So: exp(ln2+ln3)=exp(ln2)*exp(ln3)= 2*3= 6 = exp(ln6)
Till here, my work was okay.
What I didn't understand is : why should we say that the exponential function is strictly increasing over R before being able to simplify the...
I confront an integration with the following form:
\int d^2{\vec q} \exp(-a \vec{q}^{2}) \frac{\vec{k}^{2}-\vec{k}\cdot
\vec{q}}{((\vec q-\vec k)^{2})(\vec{q}^{2}+b)}
where a and b are some constants, \vec{q} = (q_1, q_2) and \vec{k} = (k_1, k_2) are two-components vectors.
In the...
Please refer to the attached image.for part
a) this is what i did:
$G = k$, $k-1< X < k$
so I substituted $k-1$ and $k$ into the given exponential rv,
this gave me
$\lambda e^{-\lambda(k-1)}$ and $\lambda e^{-\lambda k}$
$= \lambda e^{-\lambda(k-1)} + \lambda e^{-\lambda k}$
But I...
No. of Real solution of the equation ##2^x\cdot \ln (2)+3^x\cdot \ln (3)+4^x\cdot \ln (4) = 2x##
. The attempt at a solution
Let ##f(x) = 2^x\cdot \ln (2)+3^x\cdot \ln (3)+4^x\cdot \ln (4) -2x##
Here solution must be exists for ##x>0##, because for ##x\leq 0##, L.H.S>0 while R.H.S <0...
Suppose that there is initially x(not) grams of Kool-Aid powder in a glass of water. After 1 minute there are 3 grams remaining and after 3 minutes there is only 1 gram remaining. Find x(not) and the amount of Kool-Aid powder remaining after 5 minutes…
So, i set up 2 equations…
3=x(not)e^-k(1)...
find dy/dx: exy+x2+y2= 5 at point (2,0)
I'm confused with finding the derivative with respect to x of exy.
this is what I did so far for just this part: exy*d(xy)/dx
exy*(y+x*dy/dx)
do I need to put the parentheses on here? I thought so because that is the part where I used the product rule...
hello friends,
when i build the mathmatical model of robot,i face a new question that i ever seen before.
i have a reverse kinematic lever as the leg and i want to use the tip position to get the relationship of fold angle and rotate angle reversely
here is my equation:
x*e^iθ - y*e^iθ *...
Hi, I have a quick question.
Let R and S be two independent exponentially distributed random variables with rates λ and μ. How would I compute P{S < t < S + R}?
I am a little bit confused because of the variables on either side of the inequalities. I have tried conditioning on both S and R...
Homework Statement
The function T=190(1/2)^1/10t can be used to determine the length of time t, in hrs that milk will remain fresh. T is the storage temp. In Celsius
How long will milk remain fresh at 22 degrees Celsius
Homework Equations
Bases have to be same then exponents will...
Homework Statement
Suppose that the waiting time for the CTA Campus bus at the Reynolds Club stop is a continuous random variable Z (in hours) with an exponential distribution, with density f(z) = 6e–6z for z ≥ 0; f(z) = 0 for z < 0.
(a) What is the expected waiting time in minutes (the...
Homework Statement
I'm trying to solve trying logarithmic and exponential equations but for the life of me I can't seem to figure out what I'm doing wrong.
Homework Equations
Log equation: log3(x+2)+1 = log3x²+4x
Exp equation: 2x + 2x+1 = 3
The Attempt at a Solution
For the first...
Homework Statement
I want to verify
j^{-p}=e^{-j\frac{p\pi}{2}}
Homework Equations
e^{j\frac{\pi}{2}}=\cos(\frac{\pi}{2})+j\sin(\frac{\pi}{2})=j
The Attempt at a Solution
j^{-p}=(e^{j\frac{\pi}{2}})^{-p}=e^{-j\frac{p\pi}{2}}
Am I correct?
Thanks
Hi friends, i need some help for this number:
By considering the integral $$\int_{\gamma(0;1)}\exp(z) \mathrm{d}z$$,show that
$$\int_0^{2\pi}\exp(\theta)\cos(\theta+\sin(\theta)) \mathrm{d}\theta = 0$$
i know that since $$f(z)=\exp(z)$$ is holomorphic on and inside...
f(x)=x2ex
the answer is f'(x)=(x2 + 2x)ex but I don't understand how to get there.
Also I need to find g'(x) if g(x)=sqrtx(ex)
would the answer for the second one be .5x-1/2ex?
So, if we start with logarithm ln(2) assuming a base of 10, how would I solve this without a calculator?
ln(2)
10^x = 2
And I get stuck there without a calculator. I could ..
ln(10^x) = ln(2)
x ln(10) = ln(2)
x = ln(2)
But that gets me back to where I started.
So, how would I go...
just want to confirm if i did set up my integral correctly and got a correct answer.
$\displaystyle\int_0^a (e^{\frac{x}{a}}-e^{-\frac{x}{a}})$
using substitution for the first term in my integrand
$\displaystyle u=\frac{x}{a}$ $\displaystyle du=\frac{1}{a}dx$; $\displaystyle dx=adu
$
for...
[1] Total no. of real solution of the equation ##e^x = x^2##
[2] Total no. of real solution of the equation ##e^x = x^3##
My Solution:: [1] Let ##f(x) = e^x## and ##g(x) = x^2##
Now we have use Camparasion Test for derivative
So ##f^{'}(x) = e^x## which is ##>0\forall x\in...
Homework Statement
I am to find the electric field for a charge distribution of
$$ \rho(x)= e^{-\kappa \sqrt{x^2}} $$
Homework Equations
I know that gauss law is $$ \int E \cdot da = \frac{q_{enc}}{\epsilon_0} $$
The Attempt at a Solution
I am not sure what the charge...
Homework Statement
t(s) = 1 15 30 45 60 75 90 105 120 135
N(counts) = 106 80 98 75 74 73 49 38 37 22
Consider a decaying radioactive source whose activity is measured at intervals of 15 seconds. the total counts during each period are given. What is...
Homework Statement
How many oscillations occur before Mxy decays to approximately 1/3 of its initial value, for a Larmor frequency of 100 MHz and T2 of 100ms?Homework Equations
I was learning about how NMR works and about transverse relaxation.
According to what I learned, we can express...
Homework Statement
A certain type of transistor has an exponentially distributed time of operation. After testing 400 transistors, it is observed that after one time unit, only 109 transistors are working.
Estimate the expected time of operation.
Homework Equations
The Attempt...