Trig identies part 3 (part 5 if you watch the proofs)

[ilhomiee]

could you do a video on cofunctions please? :)

[brandonsuji]

your the reason i got into university

[sodaxcandy08]

i love u khan.... i always hated to remember things that i don get.. like trig identities in precalc... now that they make sense its not only fun, i can also memorize them easily.... this is gonna help me so much when i take calc ... THANK YOU KHAN!!!!! UR THE MAN!!!!!!!!

[sidcooldude443]

why is op -op but h not -h in the other triangle??

[Tetlaclava]

Fascinating

[TheDRASC14]

wait wouldn't cos(-a) be equal to -cos(a)? because although the hypotenuse remains the same( hypotenuse is never negative) the adjacent side become negative.

[7AuSrUBoY7]

@TheDRASC14 NO! the adjacent side is the same for both a AND -a... think about it :D

[madog19861]

@TheDRASC14 No, because the cos(-a) is positive. The adjacent side is still on the right side of the x-axis. Only the y value is affected by cos(-a).

[fattymole123]

You my friend, have magnificent explanation skills!

Thank you!

[x0955863233]

thanks man you helped me do my college trig homework without even ever having to go to class!!!

[ClintSevilla]

if anyone can help me with this problem it would be amazing. I don't understand how to get from the square root of the 3 to 1/2. Link to problem i51(dot)tinypic(dot)com/15hzcp­3(dot)png

[LAnonHubbard]

This is great.

[cheer4mwah]

I cannot believe im doing this stuff at 15 years old. Seriously!

[oppertunityknocks]

@cheer4mwah too bad if you got tested you would get destroyed

[cheer4mwah]

@oppertunityknocks No sir! I got dis! :)

[laker24c]

this stuff is amazing

[gentletosh7]

Can't believe i was so clueless in class when my lecturer was teaching this haha!

[IvanGangsta1]

this is really helpful!!

[MS707]

Thank you so much Mr. Khan! Your videos are helping me so much with relearning the material for the semester exam. I love how you're doing this for free. This lets students (like me) who cannot afford expensive tutors get an extra opportunity to learn.

[MRJerrod410]

I was hoping to find a proof for reducing powers of trig functions.

[bbbruke17]

thank u so much. i hope i will find move videos about calculus!

[AnimeMangaKing]

Thank You.

[mustafafaisan]

Why hypotenous foes not goes negative????

[yagonite]

Bbecause h^2= a^2 + o^2

Since the right side is all squared it means you will get a positive number therefore h^2 must be positive.

[cilution]

Think of the hypotenuse as a distance in the sense that if you were traveling in any given direction, it wouldn't make sense to say the distance traveled is negative.

In other words, if you travel 5 units in the direction 5pi/4 (225 degrees), even though in the coordinate plane, both the x and y values corresponding to the point you end up at are negative, the distance you travel can't be thought of as being negative.

[MRJerrod410]

It's because of Pythagorean's theorem: x^2 + y^2 = c^2 where 'x' is the length on the x-axis, 'y' is the length on the y-axis, and 'c' is the hypotenuse. None of these values can ever be negative.

[PersianKhavos]

love you, i love you so much im going to cut my arm and wirte you a poem with my blood !!! ^^

[Winsunn307]

This stuff is crazy hard. I wouldn't even attempt it if it wasn't for these videos.

[jokumusic]

You've thoroughly convinced me that math can be fun. I used to hate math... Trig Identities is by far the funnest thing I've played with in math so far.

[clevercleverchris]

very interesting!