GeoGebra4 is here !
This is a Java Applet created using GeoGebra from www.geogebra.org - it looks like you don't have Java installed, please go to www.java.com
Definitia functiilor trigonometrice
( cu Geogebra ! )
http://dmentrard.free.fr/GEOGEBRA/Maths/Trigono/Voircercle.html
Functia tangenta : aici