Where did trig functions come from?

[misogynisticfeminist]

I've been thought trig functions in school definitely, but never been told how were they invented in the first place! Also, is there a function like sin (theta)= something. If so, what are these functions?

 

[matt grime]

"is there a function like sin (theta)= something."

pardon? what do you mean 'like'? or something? sin is a function, it's like itself, it's 'like' a power series, is that what you mean?

 

[TenaliRaman]

Check this http://www-groups.dcs.st-and.ac.uk/~history/HistTopics/Trigonometric_functions.html.

-- AI
Another Reference : http://www.math.unifi.it/archimede/archimede_inglese/trigonometria/trigonometria/prima.html but says the same thing.

 

[misogynisticfeminist]

thanks the history part was useful.

to matt: actually what i meant was could I get a function while I substitute theta, I will get the result of sine theta without using my calculator to find sine theta of course.

 

[matt grime]

Without using a calculator? OF course not. calculate the square of 3.45234232526 without one - takes a while agreed? calculate the square of the 5#th root of 2. this is of course a question about what you mean by calculate. in this case you mean find a decimal representation of. to what degree of accuracy?

there are many ways to caculate sin, cos and many other functions as power series, called taylor or maclaurin series.

$$\sin(x)= x - \frac{x^3}{3!} + \frac{x^5}{5!}- \frac{x^7}{7!} \ldots$$

terminate after as many terms as required.