# 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

$\cos (3x) = 4\cos^3(x) -3 \cos(x)$ 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
Came across this curious identity while preparing some trigo notes. $\cos (20^\circ) \cos (40^\circ) \cos (80^\circ) =\frac{1}{8}$ According to wolfram, it is called Morrie’s Law by Feynman after his childhood friend who showed it to him. Wow, all … Continue reading