Réponses

2014-04-15T10:59:04+02:00
1) AC²=AB²+BC²
BC=AD=2
AB=2
AC²=2²+2²=8
AC= \sqrt{8}=2 \sqrt{2}

2) TanBAC=BC/AB=1
Donc BAC=45°

3) Cos45=AB/AC

4) Cos45= \frac{2}{2\sqrt{2}}=\frac{1}{\sqrt{2}}=\frac{\sqrt{2}}{2}