Trigonometry: Proof of Law of Cosines (and Pythagorean Theorem)

in hive-196037 •  2 years ago  (edited)


In this video I show a simple geometric proof of the cosine law. This is very useful in real world applications. Also from the proof of the cosine law you can easily proof the Pythagorean theorem as well by setting the angle equal to 90 degrees.

Download the notes in my video: https://1drv.ms/b/s!As32ynv0LoaIieA6mrR41UsY7jNfnw?e=EYalZT

View video notes on the Hive blockchain: https://peakd.com/hive-128780/@mes/trigonometry-proof-of-law-of-cosines-and-pythagorean-theorem

Related Videos:

Simple Proof of the Pythagorean Theorem: http://youtu.be/yt-EJlbJQp8
Trigonometry Identities: cos(x +/- y) = cos(x)cos(y) -/+ sin(x)sin(y) : http://youtu.be/VuQczhk7HOs
Trigonometry Identities: sin(-x) = - sin(x) and cos(-x) = cos(x): http://youtu.be/tD5EA2SXyFQ
Trigonometry Identities: cos and sin of angles (2p + x) and (p/2 -x): http://youtu.be/EynSefQs308
Trigonometry Identities: sin(x +/- y) = sin(x)cos(y) +/- cos(x)sin(y): http://youtu.be/edtk9thfwbM .


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I don't always prove the Law of Cosines but when I do I usually use it to prove the Pythagorean Theorem as well ;)

View video notes on the Hive blockchain: https://peakd.com/hive-128780/@mes/trigonometry-proof-of-law-of-cosines-and-pythagorean-theorem