1. 3/cos^2 24+cos^2 114.

2. Sin5x=3

3. 2cos (x/3-π/2) = 2

2*cos² (4x) - 6*cos² (2x) + 1=0

2 (2cos²2x-1) ²-6*cos² (2x) + 1=0

cos²2x = y

2 (2y-1) ²-6y+1=0

2 (4y²-4y+1) - 6y+1=0

8y²-8y+2-6y+1=0

8y²-14y+3=0

D=14²-4*8*3 = 196-96 = 100

y1 = (14+√100) / (2*8) = 24/16 = 3/2

y2 = (14-√100) / (2*8) = 4/16 = 1/4

y = cos²2x = >

0≤y≤1 = >

y = 1/4

cos²2x = 1/4

cos2x1 = 1/2; cos2x2 = - 1/2

2x1 = π/3

2x2 = 2π/3

x1 = π/6

x2 = π/3