Question

2sin x cos x = cos x 

Answer 1

2sin x cos x = cos x
ОДЗ: x∈R
2sinx*cosx-cosx=0
cosx(2sinx-1)=0
[cosx=0;          [x=П/2+Пn; n∈Z
[2sinx-1=0;      [x=(-1)^n П/6+Пn;n ∈Z

Answer 2

2sin x cos x = cos x 
2sin x cos x-cos x=0/cos x
2tdx-1=0
2tgx=1
tgx=1/2
x=arctg1/2+пn