9
(sinx+cosx-cosx-cos3x)/(cosx+cos3x)=0
sinx-cos3x=0
sinx-sin(π/2-3x)=0
-2sin(π/4+x)cos(π/4+2x)=0
sin(π/4+x)=0⇒π/4+x=πn⇒x=-π/4+πn,n∈z
cos(π/4+2x)=0⇒π/4+2x=πk⇒2x=-π/4+2πk⇒x=-π/8+πk,k∈z
cosx+cos3x≠0
2cos2ccosx≠0
cos2x≠0⇒2x≠π/2+πm⇒x≠π/4+πm/2;m∈z (общее для cos2x и cosx)
10
tgx=√3/5
x=arctg√3/5+πn,n∈z
x=arctg√3/5∈[0;72]
11
tgx=-1⇒x=-π/4+πn,n∈z
sinx=1⇒x=π/2+2πk,k∈z
x={-π/4;3π/4;7π/4;0;π/2}
-π/4+3π/4+7π/4+0+π/2=11π/4