Integral of cos^2 x

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How to integrate cos^2 x using the addition formula for cos(2x) and a trigonometric identity.
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Why does cos 2x = cos^2 x - sin^2 x

Sometimes understanding where this stuff comes from can help more than throwing out a memorized formula.

It starts with the angle addition formula
cos(A+B) = (cos A cos B) - (sin A sin B)
A=x B=x substitute into angle addition formula
cos(x+x) = (cos x cos x) - (sin x sin x) collect terms and simplify
cos 2x = cos^2 x - sin^2 x
SEAN

postholedigger
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Here is another way -- using integration by parts split this into the integral of /(cos x)(cos x)dx. Let cos x = u and cos x dx = dv. The du = -sin x dx and v = -sin x.
Then apply the formula /udv = uv - /vdu and we get = -sin x cos x -/(-sin x)(-sin x) dx = -sin x cos x -/(sin x)^2 dx = -sin x cos x -/(1 - (cos x)^2 ) dx
= -sin x cos x -/dx - / (cos x)^2 dx or 2 * /(cos x)^2 cx = -sin x cos x -/ dx +c or the final answer of - (1/2)(sin x cos x -x ) + c and since sin 2x = 2 sin x cos x
we get = - (( 1/4)( (sin 2x) - x)) + c. Relatively simple and straightforward.

thomasarch
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My eyes are bleeding, too many substitutions

davideaccorto
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Tbh, the intro music (Turkish March) made me instantly like this video. Good to see people with equally good taste in music and science. Looking forward to meeting you someday!

shishirmaharana
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That was really helpful, thanks a lot

tj_
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You could’ve just used the power reduction formula from the very beginning and factored out a 1/2 then all you have to integrate is 1/2 ∫1+cos(2x)dx Which is really easy to integrate.

davebacknolaliki
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I can see clearly now the mist is gone. Thank you sir

ZolileZicwele
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finally got what i was looking for man thanks

rishabhlakhara
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Thankyou thankyou so so so much sir 😊😊😊🦚🙏🏻🙏🏻 Hare krishna 🦚❣️❣️you cleared my huge doudt 🙇🙇🙇

SAHITY_A
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This comes to recommendation video from Youtube, thank you Youtube for knowing that I've done with every channel on my following list...

Maverick
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Let it go bro. ... U make easy things complicated.... U aren't for teaching ❤️

prakharpratapsingh
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Lmaooo I was trying to use the reduction method on this

hypnoticmoai
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Very easy question...this is a very basic question in Indian education and is taught in 11th class basics

superduper
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And why did u use the reverse chain rule ?

manishvelagala
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cos^2 x = 1/2(1 + cos2x) and then integrate simply

azmatsahi
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You're doing the lord's work, my man

georgianfishbowl
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2:24 compensate for 2x, reverse chain rule, can you elaborate and explain?
Thank You.

s-r
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shouldn't there be an easier way to do this?

angelinebena
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Dude your voice is too low.. i didn't get the point that how you've taken 1/2 from cos2x/s.. can you and anyone explain me that... PLEASE I REQUEST🙏🙏

monusonu-cm
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this is so cool
thank you dude
integration is pain

rishabhlakhara