Question

qual o valor cos 225

Answer 1

cos(225)=cos(180+45)

cos(a+b)= cosa.cosb-sena.senb

cos (180+45)=cos180.cos45 - sen180.sen45= (-1).(√2)/2 - 0.(√2)/2 = -(√2)/2

cos (225)= -(√2)/2