8 (1-sin²x)+10sinx-1=0
8-8sin²x+10sinx-1=0
-8sin²x+10sinx+7=0
8sin²x-10sinx-7=0
пусть sinx=t . t∈[-1.1]
8t²-10t-7=0 D=10²-4*8*-7=100+224=324
t1=10-18/16=-8/16=-1/2 t2=10+18/16=28/16=7/4- посторонний корень
sinx=-1/2 x=(-1)^k arcsin(-1/2)+πk. k∈Z
x=(-1)^(k+1)π/6+πk. k∈Z