Search wiring.org.co:

This example is for Wiring version 1.0 build 0100+. If you have a previous version, use the examples included with your software. If you see any errors or have comments, please let us know.

Sine Cosine.
sin() and cos(). Numbers between 0 and PI*2 (TWO_PI which is roughly 6.28) are put into these functions and numbers between -1 and 1 are returned.

    void setup()
    {
      Serial.begin(9600);
      Serial.println("angle / cos(angle) / sin(angle)");
      for (int angle = 0; angle <= 90; angle += 5)
      {
        float c = cos(radians(angle));
        float s = sin(radians(angle));
        Serial.print(angle);
        Serial.print(" / ");
        Serial.print(c);
        Serial.print(" / ");
        Serial.println(s);
      }
    }

    void loop()
    {

    }