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Tom Conlan
@tomconlan
Trig identities are beautiful once you learn to derive them. cos(a - b) = cos(a)cos(b) + sin(a)sin(b) cos(a + b) = cos(a)cos(b) - sin(a)sin(b) sin(a + b) = sin(a)cos(b) + cos(a)sin(b) sin(a - b) = sin(a)cos(b) - cos(a)sin(b) It is more helpful to copy out the derivations than to copy out the identities themselves.
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Sine
@sinusoidalsnail
Yeah! Absolutely better to derive as much as possible, and become fluid with them as you would with language etc
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Vitalik Buterin
@vitalik.eth
It's even more beautiful once you realize that those rules are just the real and imaginary parts of complex number multiplication! (a+bi)(c+di) = (ac - bd) + (ad + bc)i The real part is the cos formula, the imaginary part the sin formula
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