4)
sin (pi + 3x/4) - sin (3pi/2 - 3x/4) = 0
- sin (3x/4) + cos(3x/4) = 0 /: cos(3x/4) ≠ 0
tg(3x/4) = 1
3x/4 = pi/4 + pik / *4/3
x = pi/3 + 4pik/3, k ∈Z
5) 3sin^2x - 4sinxcosx + 5cos^2x = 2
sin^2x - 4sinxcosx + 3cos^2x = 0 /: cos^2x ≠ 0
tg^2x - 4tgx + 3 = 0
(tgx - 1 )(tgx - 3 ) = 0
x = pi/4 + pik, k∈Z
x = arctg(3) + pik, k∈Z