Maths - Integration


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Flashcards

What is $x^n$ integrated?


\[\frac{x^{n+1}}{n+1} + c\]

What is $kx^n$ integrated?


\[\frac{kx^{n+1}}{n+1} + c\]

Integrate $2x+4$?


\[x^2 + 4x + c\]

What does $c$ mean in integration?


The constant of integration.

Why is a constant of integration important?


Because it represents any constant term that would disappear when being differentiated.

What does it mean to find a particular solution of an integral?


Calculating the actual value of an integral but solving for the constant of integration.

If a general solution specifies a family of curves, what does a particular solution specify?


A single curve.

If you have a general solution to an integral and is told that the solution passes through a point, what are you then finding?


A particular solution.

If $\int 2x+4 dx = x^2 + 4x + c$ but the actual solution passes through $(1,9)$, how can you solve for $c$?


\[1^2 + 4 \times 1 + c = 9 \\\\ 1 + 4 + c = 9 \\\\ 5 + c = 9 \\\\ c = 4\]

What’s the flow chart process for finding a particular solution to an integral?


\[\text{integrate} \to \text{substitute} \to \text{solve}\]

What is the first step for evaluating an integral $\int^b _ a$?


Finding the antiderivative/indefinite integral $F(x)$.

If $f(x)$ is a function, what is the notation for the antiderivative of $f(x)$?


\[F(x)\]

When evaluating $\int^b _ a$, what do you do with $F(x)$?


\[F(b) - F(a)\]

How can you visualise $F(b) - F(a)$ when finding the area under a curve?


Finding the area up to the upper bound $b$ and then subtracting the unneccesary area up to $a$.

Why does the integral symbol look like $\int$?


It’s like a long S shape, representing a sum.

2021-06-09

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\[\int \tan x dx\]

What is this equal to??

\[\ln(\sec x) + c\]
\[\int \tan x dx\]

What is this equal to?


\[\ln(\sec x) + c\]

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\[\int \cot x dx\]

What is this equal to??

\[\ln(\sin x) + c\]

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\[\int \sec x dx\]

What is this equal to??

\[\ln(\sec x + \tan x) + c\]

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\[\int \csc x dx\]

What is this equal to??

\[\ln(\csc x - \cot x) + c\]

2021-07-03

What’s another way of writing $\ln(\sec x) + c$?


\[-\ln(\cos x) + c\]
\[\int \cot x dx\]

What is this equal to?


\[\ln(\sin x) + c\]
\[\int \sec x dx\]

What is this equal to?


\[\ln(\sec x + \tan x) + c\]

2021-12-15

\[\int \csc x dx\]

What is this equal to?


\[\ln(\csc x - \cot x) + c\]

What is $\sin^2(x)$ in terms of $\cos(2x)$?


\[\frac{1}{2} (1 - \cos(2x))\]

What is $\cos^2(x)$ in terms of $\cos(2x)$?


\[\frac{1}{2} (1 + \cos(2x))\]

How can you integrate $\cot^2 x$?


Rewrite as

\[\csc^2 x - 1\]

2022-01-08

What is the formula for the area between the $x$-axis and a parametric curve defined with $x = f(t)$ and $y = g(t)$?


\[\pi \int^{t = p} _ {t = q} y \frac{\text{d}x}{\text{d}t} dt\]

What is the formula for the area between the $y$-axis and a parametric curve defined with $x = f(t)$ and $y = g(t)$?


\[\pi \int^{t = p} _ {t = q} x \frac{\text{d}y}{\text{d}t} dt\]

2022-01-19

If you normally use $\int y \text{d}x$ when finding the area between the $x$-axis and a curve, how would this change for integrating parametrically?


\[\int y \frac{\text{d}x}{\text{d}t} \text{d}t\]

If you normally use $\int x \text{d}y$ when finding the area between the $y$-axis and a curve, how would this change for integrating parametrically integrating parametrically?


\[\int x \frac{\text{d}y}{\text{d}t} \text{d}t\]

2022-04-12

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\[\int \sin(4x) (1 - \cos 4x)^3 \text{d}x\]

You could overcomplicate this by using several different trig identities and expanding. What could you also do?? Just notice that the derivative of the $\cos$ part is the four times the $\sin$ part.

2022-04-17

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\[\int \frac{1-t^2}{1+t^2} \text{d} x\]

How should you tackle this?? Algebraic long division.

2022-05-11

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\[\int \frac{3x}{\sqrt{4-x^2}} \text{d}x\]

How do you integrate this?? Consider

\[\frac{\text{d}}{\text{d}x} \sqrt{4-x^2}\]
Why is
\[\int \frac{3x}{\sqrt{4-x^2}} \text{d}x\]

equal to

\[3\sqrt{4-x^2}\]

and not

\[-\frac{3}{2} \sqrt{4-x^2}\]

?? Because the $-\frac{1}{2}$ comes from the power rule and the chain rule.

2022-05-30

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\[\int\frac{x^2}{1 + 16x^2}\text{d}x\]

How would you tackle this?? Algebraic long division.

2022-06-06

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\[\lim _ {\delta x \to 0} \sum^6 _ {x = 2} \frac{1}{x} \delta x\]

Can you write this as an integral??

\[\int^6_2 \frac{1}{x} \text{d}x\]

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\[\int^10 _ 3 3x^2 - 4 \text{d}x\]

Can you rewrite this as the limit of a sum??

\[\lim_{\delta x \to 0} \sum^{10}_{x \to 3} (3x^2 - 4) \delta x\]

2022-06-07

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\[\sin 6x \sin 8x\]

Rather than integrating by parts, how could you rewrite this in order to help with integration??

\[\frac{1}{2}\left( \cos(2x) - \cos(14x) \right)\]



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