Question

dados e= cos 2x + cos x/5 - cos x/15 e x= 5.pi dividido por 2

Answer 1

Do enunciado temos:

$e=cos(2x) + cos (x/5) - cos(x/15)--\ \textgreater \ para,x= \frac{5 \pi }{2} \\ \\ e=cos ( 2\frac{5 \pi }{2}) + cos ( \frac{5 \pi }{2}/5) - cos ( \frac{5 \pi }{2}/15) \\ \\ e=cos(5 \pi )+cos( \frac{5 \pi }{10})-cos( \frac{5 \pi }{30}) \\ \\ e=cos(5 \pi )+cos( \frac{ \pi }{2})-cos( \frac{ \pi }{6}) --\ \textgreater \ em,graus \\ \\ e=cos900^{o}+cos90^{o} -cos30^{o} \\ \\ e=cos180^{o} +cos90^{o}-cos30^{o} \\ \\ e=-1+0- \frac{ \sqrt{3} }{2} \\ \\ e=-(1+\frac{ \sqrt{3} }{2} )$