cos(L+П/3)+cos(П/3-L)= cosLcosП/3 - sinLsinП/3 + cosП/3cosL + sinП/3sinL =
A*A * A*A*A*A*A*A/A*A*A*A=A*A
Решение
(x+18y)²−(18x+y)² = ( x + 18y - 18x - y)*(x + 18y + 18x + y) =
= (- 17x + 17y)*(19x + 19y)