1)сos 2t/(cost+sint)-cost=cos²t-sin²t)/cost+sint -cost= (cos²t-sin²t-cos²t---sint*cost)/cost+sint=-sint(cost+sint)/cjst+sint=-sint
2) cos8x-cos6x=0 2sin8x+6x)/2*sin(6x-8x)/2=0 2sin7x*sin(-x)=0
sin7x=0 7x=πn. n∈z x=πn/7 n∈z
sin(-x)=0 -sinx=0 sinx=0 x=πm. m∈z
4) sin72+cos(180+44)-sin12=(sin72-sin12)-cos44=2sin(72-12)/2cos(72+12)/2-cos44=
2sin30*cos44-cos44=cos44(2*1/2-1)=cos44*0=0