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0 pointspeterfirefly5mo ago0 comments

How do you remember sin and cos in practice? Draw a unit circle, draw a radius at whatever angle with the x axis that you want. The point where the radius touches the perimeter has the coordinates cos(angle), sin(angle). How do you remember the order? Alphabetically, just like the Baltic states.

Tan is the slope of the radius line: sin(angle)/cos(angle).

How do you remember the fraction for the slope of a line? I use a mnemonic: dydx ("dydex").

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SoftTalker5mo ago

> How do you remember sin and cos in practice?

I draw on the ratios I memorized in high school, e.g. sin=opposite/hypotenuse, but 40+ years later sometimes I'm not sure so I look it up online.

My needs for trigonometry are separated on a scale of years, and at some point knowledge unused is knowledge forgotten.

antod5mo ago

Since high school in the 80s I still remember the phonetic mnemonic "soh cah toa" one teacher mentioned off the cuff once.

sine is opposite over hypotenuse

cosine is adjacent over hypotenuse

tangent is opposite over adjacent

peterfireflyOP5mo ago

The unit circle diagram is nicer because it naturally works with angles bigger than 180 and negative angles. If you look at the unit circle with a radius and the intersection point with the circle, you naturally get a right triangle of the kind your mnemonics apply to.

It also has the advantages of being language/culture blind.

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