Cos x cos П/4 - sin x sin П/4=1

Question

Cos x cos П/4 - sin x sin П/4=1

Answer 1

Формула: cos(a+b)=cosa*cosb - sin a*sinb

cosx*cos π/4 -sinx*sin π/4=1
cos(x+π/4)=1
x+π/4=±arccos1+2πn, n € Z
x+π/4=π/2+πn, n€Z
x=π/2-π/4+πn, n € Z
x=π/4+πn, n € Z -ответ