Question

Calcule A  sabendo que A=cos3x e x=5pi/2 rad ? URGENTE

Answer 1

$A=cos 3x \\ \\ x= \frac{5 \pi }{2} \\ \\ a=cos 3.\frac{5 \pi }{2}} \\ \\ a=cos \frac{15 \pi }{2}} \\ \\ a=sen( \frac{ \pi }{2} -\frac{15 \pi }{2}) \\ \\ a=sen( -\frac{14 \pi }{2}) \\ \\ a =sen(-7 \pi ) \\ \\ a=-sen(7 \pi ) \\ \\ a=sen(6 \pi + \pi ) \\ \\ a=sen6 \pi +sen \pi \\ \\ a=sen(3.2 \pi )+0 \\ \\ a=3sen2 \pi \\ \\ a=3.0=0$