Question

решите уравнение
а) 3 sin^{2}x + 7cosx -3=0
б) sin^{2}x - cos x sinx =0

Answer 1

1) 2-2cos^2 x - 7cos x + 2 = 0

-2cos^2 - 7cos x + 4 = 0

D=49+32=81

cosx=1/2

x=+-п/3 + 2пn

2) cosx*(cosx+sinx)=0

cosx=0

x=п/2+пn

cosx+sinx=0

tgx=-1

x=п/4+пn