Law of cosines | Trig identities and examples | Trigonometry | Khan Academy

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Son: Hey Dad, why is my sisters name Rose?
Dad: Because your mother loves Roses.
Son: Oh ok thanks Dad
Dad: No problem, Law of cosines | Trig identities and examples | Trigonometry | Khan Academy

Jacks.Outback

This is a life saver bc I’m forgetting everything during quarantine.

crow

This 4 min video saved me a half hour of listening to my teacher’s lecture. Thanks Mr Khan!

davidkhamush

I have a test today on this but now I think I’ll pass it

TrioArtsOfficial

omg I'm glad I found this, my teacher won't teach properly to the online students so I have had to teach myself

elorasimonson

what program are you using to write things down?

sulhogar

I really appreciate your kindness and effort sal khan. :D you're the reason I got high grades

jeromecolico

Thank you so much for explaining this problem!!! :)

nathalieroberts

You don't have to hit the "times" key before the function key. It's built into the circuitry. So you can just punch in, for example, 2sin(45) or 3cos(60). Saves keystrokes. Also, I just go straight to square root when solving for a side and straight to arccos when solving for an angle.

cobyup

How about if C side is missing

Do i still use the
A²= B²+C²-2BC (CosA)

??

patzer

I love ur videos soo much, they help me soo much
Thank you

Jeonify_

Thank you so much. This video helped a lot!

madelinechambers

What do you do if youre looking for one of the angles?

gamefreaker

The fact that Sal paused in the beginning to see if I would derive the Law of Cosines spontaneously from first principles made me laugh out loud. It really is a thing with math-brained people. Imagine joining the army and having an instructor show you mechanical diagrams and principles of gas-operated feeding mechanisms, then hand you a specific rifle and expect you to derive the manual of arms on your own. Thankfully, only math people are like this lol. Love Khan Academy though don't get me wrong.

survivethevibe

Can we do this by this method, i worked a little bit around angle ration and end up with this formula a = and got identical answer ?! And what this this method is called if it exist?

lenkastranjakovic