Sine and Cosine Addition Formula Proof

A proof of sin (A+B) and cos(A+B) formulas for acute A and B.

[somethingkabir]

The best and most easy and logical proof!!! Thank you 😊

[jackflash]

I agree this is the best proof I've seen on you-tube. When people draw circles with unit 1 radius to recreate that same digram, you 'can't see the woods for the trees' . You drew one triangle on top of the other and all of a sudden it is clear as day.

[samakolBanbol]

I don't care about proofs, but I needed to understand visually why adding or subtracting angle ratios is done thusly and I looked at the proof somewhere else but couldn't understand it... Now I understand exctly and what's happening and I don't even need to memorize anything about compound angles.. I can draw it on the spot and derive what I need even 10 years from now!! Thank you Erik!

[newwavenewwave]

It's great to finally see a video that demonstrates several trig formulas in one diagram only. Not even to mention that if one masters that he can hence easily get a great bunch of related trig identities

[Takatsu_Jie]

I have a good maths teacher but his explanation was really confusing but your maths vid broke it down into tiny steps which made it so much easier to digest thank you👍

[MillValleyBoczeks]

Hey, you were that smart kid in my Calculus 101 class in Ithaca 40 years ago. I see that you found your calling! Well done.

[raminrasouli]

This was the best video I have seen about this proof. Thank you.

[descendantt]

It's the simpliest proof I've ever seen. Thank you so much!

[redfinance]

Very good Proof, thank you. I prefer this one rather than the one will a lot of fractions and assumptions, this one is much cleaner and well defined.

[fomalhautXP]

If there are talent of teaching, this is what it is. Thank you so much for easy explanation.

[frankhong]

Wow, that's hella intuitive. So intuitive that it was forever written into my gene!

[eniangeniang]

this guy is good. big ups man. this is the simplest proof i've ever seen on this topic

[MohitSharma-gpht]

This channel deserve millions of followers

[TheALEXMOTO]

That's the best explanation I've seen in years.

[Sam-fqho]

Completely brilliant. Thank you so much!

[saidndimbwa]

This is easiest way of this proof...you are genuine! Live long!

[sajidrafique]

I went through 4-5 videos ...Yours is BEST

[rnd_penguin]

As someone who was struggling to figure out this shit, this video is a godsend for me.

[fordtimelord]

Just a basic knowledge of complex numbers and Euler’s formula makes this proof almost trivial. But fascinating see the traditional real method.

[vaishnavi]

really simple diagram-much easier to understand than other diagrams-thank you