Sin4x + sin18x =0; [ sin18x+sin4x =0 ].
2sin(4x+18x)/2*cos(4x-18x)2= 0;
2≠ 0;
sin11x*cos7x=0 , [ cos(-α) =cosα ] ;
sin11x=0 ⇒ 11x = π*k ; x= (π/11)*k ;
cos7x = 0 ⇒7x =π/2 + π*k ; x= π/14 + (π/7)*k ; k -целое число.
Операция: деление
множества: натуральных чисел
{x/10 - y/5 = 0 | * 10
{5x + y = 7 | *6
{x - 2y = 0
{10x + y = 42
{x = 2y
{20y + y = 42
{x = 2y
{21y = 42
{x = 2y
{y = 2
{x = 4
{y = 2