Trigonometry Identities: cos(x +/- y) = cos(x)cos(y) -/+ sin(x)sin(y)

in MES Science18 days ago (edited)

In this video I derive addition and subtraction identities, cos(x+y) and cos(x-y), using the Law of Cosines and the Pythagorean Theorem. This identity is very useful in all of mathematics and is used in the derivations of many trigonometric derivatives and integrals.

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Trigonometry Identities

Trig - Sub Add cos(x+y) Resized AI.jpg

Cosine Addition and Subtraction Formulas

Subtraction: cos(x-y) = cos(x)cos(y) + sin(x)sin(y)




Addition: cos(x+y) = cos(x)cos(y) - sin(x)sin(y)


Combining Addition and Subtraction Formulas



I will need to invite my daughter, maybe she will come in handy :)
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