1 + 2cos3xcosx - cos2x = 0
2cos3xcosx = 2(cos(3x+x) +cos(3x-x))/2= cos4x+cos2x
1+cos4x+cos2x-cos2x=0
1+cos4x=0
cos4x=-1
4x = пи +2пи*n
x =пи/4+ (пи/2)*n
Решение!!!!!!!!!!!!1111111111
S=a*b*sinα.
a=9
b=14
sinα=30 ⇒ 1/2
S=9*14*0.5=126*0.5=63см²
1) ( 3 ^ 2 ) ^ - 6 = 3 ^ - 12
2) ( 3 ^ 3 ) ^ 5 = 3 ^ 15
3) 3 ^ - 12 • 3 ^ 15 = 3 ^ 3
4) 3 ^ 3 : 3 ^ 4 = 3 ^ - 1 = 1/3
Ответ 1/3