Bonsoir,
On a :
[tex]A = \frac{\cos \left(\frac{19\pi}{4}\right)}{\sin \left(\frac{15\pi}{6}\right)}\\
A = \frac{\cos \left(4\pi + \frac{3\pi}{4}\right)}{\sin \left(2\pi + \frac{\pi}{2}\right)}\\
A = \frac{\cos \left(\pi - \frac{\pi}{4}\right)}{\sin \left( \frac{\pi}{2}\right)}\\
A = \frac{-\cos \left( \frac{\pi}{4}\right)}{\sin \left( \frac{\pi}{2}\right)}\\
A = \frac{-\frac{\sqrt 2}{2}}{1}\\
A = -\frac{\sqrt 2}{2}[/tex]
Si tu as des questions, n'hésite pas ! =)
