Respostas

2014-05-19T00:05:55-03:00
cos(x- \frac{\pi}{2} )=1

sabendo que 
cosseno de um arco completo (360°) é  = 1
cos(2π) = 1
cos(360°) = 1

π= 180
2π =360

temos 

x- \frac{ \pi }{2} =2 \pi \\\\ \frac{2x- \pi }{2} =2 \pi \\\\2x- \pi =2 \pi *2\\\\2x- \pi =4 \pi \\\\2x=4 \pi + \pi \\\\2x=5 \pi \\\\x= \frac{5 \pi }{2}