Réponses

2014-05-14T12:03:47+02:00
Cos²a+sin²a=1
Sin²a=1-cos²a
Sin²a=1-(-1/5)²
Sin²a=1-1/25=24/25
Sina= \sqrt{ \frac{24}{25}} = \frac{ 2\sqrt{6}}{5}