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Mathematics 14 Online
OpenStudy (anonymous):

Integrals

zepdrix (zepdrix):

\[\Large\rm \cos \theta\left[\frac{\sin \theta}{\cos \theta}+\frac{1}{\cos \theta}\right]\]Distribute the cos theta, should simplify things down quite a bit.

OpenStudy (anonymous):

so \[\frac{ \cos(\theta)\sin(\theta) }{ \cos(\theta) }+\frac{ \cos(\theta) }{ \cos(\theta) }\]

OpenStudy (anonymous):

The cos's cancel each other leaving sin(theta)+1 ?

zepdrix (zepdrix):

Mmm yah looks good! Understand how to integrate those two terms?

OpenStudy (anonymous):

I know how to do it without the trig functions, first time seeing them with integrals

zepdrix (zepdrix):

When you take derivatives of your sine function it follows this pattern that I'm sure you're familiar with:\[\Large\rm \sin x\to \cos x\to -\sin x\to -\cos x\]And then it repeats that process. Errr lemme show just a few more on each side,\[\Large\rm -\cos x\to\sin x\to \cos x\to -\sin x\to -\cos x\to \sin x\] For integrating we just go backwards:\[\Large\rm -\cos x\leftarrow\sin x\leftarrow \cos x\leftarrow -\sin x\leftarrow -\cos x\leftarrow \sin x\]

zepdrix (zepdrix):

So for sine, it just brings us back to uhhhh -cosine, yes?

OpenStudy (anonymous):

right

OpenStudy (anonymous):

so it would be x - cos(x)

zepdrix (zepdrix):

Yah good job! With some type of +C on the end if you want.

OpenStudy (anonymous):

right, yeah. Thanks!

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