Ответ:
-18×25+18×31=18(-25+31)=18×6=108
98|18
90|5
—
8ост
98÷18 = 5 (ост 8)
Cos x/4*sin π/5-sin x/4*cosπ5=-√2/2Cos x/4*sin π/5-sin x/4*cosπ/5 = -(√2)/2 ;
Cos( x/4+ π/5) = -(√2)/2 ;
x/4+ π/5 = + ,-3π/4 +2π*n ;
x+ 4π/5 = + ,-3π +8π*n , n∈Z.
x = (+,-) 3π - 4π/5 +8π*n , n∈Z.
x₁ =11π/5 + 8π*n , n∈Z ;
x₂ = -19π/5 + 8π*n , n∈Z.
ответ :11π/5 + 8π*n ,-19π/5 + 8π*n , n∈Z.