35.
sin5x - sin3x = 0
2 * sin((5x-3x)/2) * cos((5x+3x)/2) = 0
2 * sinx * cos4x = 0
sinx = 0
cos4x = 0
x = πn
4x = π/2 + πn
x = πn
x = π/8 + πn/4
n ∈ Z
36.
cos4xcos5x + sin4xsin5x = √3/2
cos(5x - 4x) = √3/2
cosx = √3/2
x = π/6 + 2πn
x = -π/6 + 2πn
n ∈ Z