Réponses

2014-05-07T15:25:48+02:00
On developpe ( cos(a) + sin (a) )² = (cos(a))²+2×cos(a)×sin(a)+(sin(a))²  et on a  cos² (a) + sin² (a) = 1 donc  c'est  1+2×cos(a)×sin(a)