1. ## Original sin()

Hello,

Does anyone know how the sin() function works, i.e. how it finds the sine of the input angle computationally?

2. I don't know for sure, and have nothing to back me up, but I'd bet it's a fairly simple lookup system, probably based on the repetitive nature of the unit circle.

3. My guess would be that it uses the power series equivilant of sin(x)... I think I heard somewhere that's how a calculator finds it. But that's just a guess.

4. Triangle ABC has three sides AB, BC and AC. If ABC is a right angle triangle, then Sin(A) = BC/AB ...(sin(x) = opposite / hypostenuse). There is only one hypotenuse so naturally, A != 90 degrees.

5. Well, you could go that route if you're familiar with calculas but I think the basics still apply. It's been been too long since I've looked at that kind of Math...lol

This should be sufficient.
http://library.thinkquest.org/10030/2trigfu.htm

6. Lookup tables
Polynomial expansion
Maths co-processor instruction

All viable ways depending on your individual circumstances of the need for speed, accuracy and available processing power.