16-64х=0
-64х=-16
64х=16
х=16/64
х=0.25
Ответ:0.25
1)cos4x • cos5x – cos(4x + 5x) = 0;
cos4x • cos5x – cos4x • cos5x + sin4x • sin5x = 0;
sin4x • sin5x = 0
sin4x = 0 → x = πn/4; N∈Z
sin5x = 0 → 5x = πk → x = πk/5; K∈Z.
2)соs⁴a + sin²a • cos²a;
cos²acos²a + sin²acos²a;
cos²a(cos²a + sin²a);
cos²a • 1 = cos²a.