Proof of the cosine rule

How to prove the cosine rule using a geometric argument.

[NomthandazoAmaraSithole]

, my teacher's method was so long and confusing, Thank you soooo much, You are the best!

[thalithanemutudi]

Where were you when I thought the cosine rule rule was hard to prove ?😭
Thank you so much sir, this was soo easy to understand ❤

[CamMathsTutor]

Really nice and simple, love it!🙂 Keep up the good work

[mrteiijr]

Your explanation is so easy to understand. Thank you very much for the video.

[SeegalMasterPlayz]

This was interesting to know about. Thanks for sharing the proof with us.

[masashibata]

The proof presupposes Pythagoras theorem which is a special case of the law of cosines, making it somewhat a circular argument. There is a proof without using Pythagoras theorem from more basic principles of Euclidean geometry.

[eipimath]

Thanks for sharing! I posted a short video on deriving the law of cosines, It should apply for all angles (acute, obtuse, reflex, negative). Hope to get your thoughts.

[MenLette]

Hi I have a question, why do you subtract equation 1 and 2 together apart from trying to get rid of h^2. How does it make actual conceptual sense, what is it showing exactly?

[apxmath]

Thanks for the proof... I never really found interest in the actually proof after I was thought when and where it was applied... thanks cheers mate

[dr.rahulgupta]

Why you have not put h^2=b^2--x^2 in eqn 2? This directly gives the required result which you want .make steps simple.

[richarddavy-smith]

Had to stop watching. You can’t say the letter h correctly.