25sin^x+30sincosx+9cos^x=0

cgc

спс

25sin²x + 30 sinx cos x + 9cos²x = 0

(5sin x + 3cos x)² = 0

5sin x + 3cos x = 0 |:cos x≠0

5tg x + 3 = 0

tg x = -3/5

x=-arctg(3/5) + πn,n ∈ Z