Trig: Double-Angle Formulas

[SuperPowerFighter]

lol i m dumb in mathematic but i get it...LOL THANK YOU!!!

[TheChunggg]

Lol I just learned this lesson in less than 5 minutes, and it was more effective than my actual advanced functions class -.-

[arber622]

as soon as he says "lets take a look at our first problem" and smiles...i know im going to be ok

[OrangeJuiceeee]

OMG YOU MAKE IT LOOK LIKE MAGIC!!!!!!!

[1piecemage]

So*

[ratifyequality]

@1piecemage hahaha you can't spell!

[1piecemage]

@ratifyequality ?

[1piecemage]

Bahaha this is soon easy

[bossman8603]

Thanks to mathTV and KhanAcademy I'm learning more online than in class.

[sarablack10]

Thank you very much!!! You are very clear, easy to follow, and straight to the point. Thank you so much. I wish you were my teacher!

[ZecellonTech]

What if you have cos4x? what is it's equivalent?

[ManDudeYeah]

@ZecellonTech Yea, I don't get it either, dude.

[a0last0request]

YOU ARE HOLYYY. SAVED

[MistressSerenity]

You are my Jesus.

[hoiningt]

u saved me from misery! wish ur my maths teacher 

[rawna1]

very helpful, thanks!

[YesImTheBest757]

Omg thank you for this video. SO helpful. My book makes everything so much more complicated than it really is.

[Killuminatismd]

Men i have love for: (no homo)= This man. PatrickJMT. KhanAcademy. They are brilliant mathematicians that deserve recognition. Good job. You are better than our teachers! (Y)

[Transpacity]

@Killuminatismd I beg to differ - they're great teachers but they're not mathematicians....a mathematician is someone who DOES math. These guys just teach it. Look up what a mathematician is...you don't need to be good at "school math" to be a mathematician.

[halovir]

@Killuminatismd hey they are my youtube teachers too! :D

[rampage222555]

I learned more in these 4 minutes than I did in the hour long class. I didnt sleep last night because I was studying for todays exam, and the best part is that I dont remember anything...

[4ourTimber]

This helped me a lot!!! My teacher sucks!!!!

[veronicachic]

and without youtube, i would be failing.....big time...

theres no point in me even going to class, when i can stay home and learn so much better from these guys <3

i love you :X

[cheyennemcnizzle]

Why can't we have teachers like this nowadays?! Gosh, without this guy i would be failing right now! THANKYOU FOR YOUR AWESOMENESS! YOU ARE THE MATH WIN WIZARD!

[veronicachic]

am i the only one that's turned on by this video 0_0

[WudULikeFriesWitThat]

@veronicachic No you're not lol. Multiple lightbulbs are going on inside my head.

[XxAngelShinn]

you got very neat writing and yet u write fast too wow =/.... way better than my teacher

[flyinganimepig]

double angles all the way, cross the whiteboard, yeah, yeahhhhhh!! so intense.

[Snazz15]

Wow thank you i completely understand it and more i like how you made the graphing problem simple

[bevon17]

Im subscribing god damnit!

this guy is epic

I'm learning more from this guy than my teacher that I pay for

SCHOOL IS A SCAM!!... I want my degree From Youtube University

I go to YU....... what school do you pay 15k a semester to go to???

oh UW??

haha sucks for you

[goku21060]

@bevon17 XD!!!!!!

[Iamrealify]

You are amazing.

[Imakeplanesboom]

i need helppppp

[ammarhollywood]

woow I love this guy

[TheBoiFlip]

this guy got me from a C to an A in my math class

[palixxbeauty]

@gemgem92 yes there is

we can prove that idenity by using another idenity which is the sum idenity for sin. and since the sum indentity for sin is= sin (A+B)= sinA cosB + cosA sinB

Sin2A is the same as Sin(A+A) which would then be equal to

sinA cosA + cosA sinA.... and that is the same as 2sinA cosA

=D

[palixxbeauty]

@gemgem92 its just one of the double angle identities that u should memorize to do these problems. :)

[dewi20]

thanks

[ElizabethJumz]

Thanks...hopefully this will help with c4 :)

[frozenpyre]

Just wanted to say this was extremely helpful. Maybe the U.S. government could save a few bucks by using these videos instead of teachers.

[bigboycory2]

its called an identity not expanded form

[Logictech111]

Omg this is so helpful. 5/5

[sergiorenegarcia]

Thank you!!! You teach so much better than my teacher. Thank you for making this because it's going to help me on my test. keep up these videos

[iLoveBrucas13]

thank you :)

i have my test on this tomorrow !

[Smieling]

fantasic teaching :D

[Blueknightex]

Omfg what!? I'm watching a video of something that my Maths teacher didn't even teach me when we were doing

Trigonometry Double Angle Formulus!!

[marcusjhung]

great explanation

[brownsugah305]

OMG thank you so much for this video I was soooo confused and you broke it down for me thank u thank u thank u tons!!!!

[salviileo]

OMG Thanksz for this video !!!

I passed the Math B regents Exam !

Thank You !

[salviileo]

you're excellent !!!!!!!!!!

Thanks :D

Now I won't fail the Math B regents this June >:]

[iceebob21]

holy!

i can actually read his writing!

[SwoonForMe]

this is amazing.

(great bonus with the fact that he can draw straight lines and has nice writing)

[cwilli500]

wat a bro

[SkiddyMarks]

what age do you this stuff at in america?

[supermoddavid]

i did it in 10th grade. 15-16 yrs old.

[chao5cuber]

I'm in Calc 2 in 10th grade and I'm 14 so please don't brag

[supermoddavid]

First off, I wasn't bragging, he simply asked what age we do it and I told him. Second off, you are not in Calc 2 in 10th grade @ age 14. Please understand people's comments before posting.

[ChristianTypeR]

My friend is in Calc 2 in 9th grade :O

[brownsugah305]

I have tenth graders in my mac 1147 class in college so it is possible

[Blueknightex]

Hmm... at first I was shocked to hear the word"grade" but anyways that's competely normal. At our country we do calculus at 1st-2nd year of senior high school.

[Ebaum744]

I just learned it this year, grade 12.. lol

[marniemarie1]

same

[Subaru537]

me too.

[wlryn6]

thank you so much this has helped quite abit

[cutay51]

lol. this may be odd, but i really like your handwriting, so neat unlike most of my math teachers hahah

[Khaleelyhaji]

Wow man I love this. I probobaly will never have to open my notes again.

YouTUbe FTW

[animallovervet09]

Thanks to you tube I won't fail my test tomorrow! No thanks to my professor of course :(

[NellyMath]

Never rely on professors. It's up to you to learn from practice and other sources of information like you found here. :)

[guyanaprincess66]

i wish youtube was available on school computers :/

[snoopster2009]

This is a good man!!!

[arrrprivate]

i am learning more from youtube than my professor...

[brendanb89]

True that!

[Ade161]

@arrrprivate which is sad

[kraftytoo]

@arrrprivate amen to that. *choir of angels singing* ahh! I got it! ;)

[qaHs0r]

@arrrprivate Same here. :D

[nanohark]

Again, thx.

[marlon8080]

You? You're good. Real Good.

[13loodLust]

I LOVE U

U SAVED MY ASS!

[genericvideo1]

I'm sure whatever book you've written is better than our classes. Trigonometry sixth edition by charles p. mckeague and mark d. turner.

[genericvideo1]

Just to clarify I was recommending professor McKeague's book not saying its the bad one. I'm a triathlete so I love all the cycling references.

[LTF85199]

sweeet sooooo simpleeee my teacher made this look sooooo haaaaaaaard

[aulakh1989]

why are you so awesome?????

[Waranle]

Again another good video, thank you Sir

[maylien]

Thanks, I will show this to my Pre-Calc students today!

[aeternuslibertas]

BRAVO!!! So clear !!!