Category Archives: Trigonometry

Fake curves

Interesting post on how a supposed trig function is actually not trig. I have to admit I used to do things like this and use the arc tool (on powerpoint) to create curves that only look vaguely like the actual … Continue reading

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Mnemonic Trig (or Trick)

[tex]\cos (3x) = 4\cos^3(x) -3 \cos(x)[/tex] The way to remember it in Hokkien (a local dialect commonly spoken in Singapore, Taiwan and southern parts of China): Cor Sah ($1.30) = Si Cor Sah ($4.30) – Sah Cor ($3). You can … Continue reading

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Morrie’s Law

Came across this curious identity while preparing some trigo notes. [tex] \cos (20^\circ) \cos (40^\circ) \cos (80^\circ) =\frac{1}{8} [/tex] According to wolfram, it is called Morrie’s Law by Feynman after his childhood friend who showed it to him. Wow, all … Continue reading

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