a) sin7x\2 + cos 7x\2 = 1
b) cos2x + sin2x + 2cos^2x=0

A) 2sin 7x/4*cos7x/4+cos^2 7x/4-sin^2 7x/4=cos^2 7x/4+sin^2 7x/42sin7x/4*сos7x/4-2sin^2 7x/4=0 /разделим всё на cos^2 7x/4, ≠02tg7x/4-2tg^2 7x/4=0tg 7x/4(1-tg7x/4)=01)tg7x/4=0 - частный случай7x/4=pn, n∈Zx=4pn/7, n∈Z2) 1-tg7x/4=0tg7x/4=1х=p/7+4pn/7, n∈ZB) cos2x=cos^2x-sin^2xsin2x=2sinxcosxcos^2x-sin^2x+2sinxcosx+2cos^2x=03cos^2x+2sinxcosx-sin^2x=0 /делим всё на cos^2x≠03+2tgx-tg^2x=0(tgx-3)(tgx+1)=01) tgx=3x=arctg3+pn, n∈Z2) tgx=-1x=-p/4+pn, n∈Z

А2sin(7x/4)cos(7x/4)+cos²(7x/4)-sin²(7x/4)-sin²(7x/4)-cos²(7x/4)=02sin(7x/4)cos(7x/4)-2sin²(7x/4)=02sin(7x/4)*(cos(7x/4)-sin(7x/4))=0sin(7x/4)=0⇒7x/4=πn⇒x=4πn/7,n∈zcos(7x/4)-sin(7x/4)=0/cos(7x/4)1-tg(7x/4)=0⇒tg(7x/4)=1⇒7x/4=π/4+πn⇒x=π/7+4πn/7,n∈zБcos²x-sin²x+2sinxcosx+2cos²x=0/cos²xtg²x-2tgx-3=0tgx=aa²-2a-3=0a1+a2=2 U a1*a2=-3a1=-1⇒tgx=-1⇒x=-π/4+πn,n∈za2=3⇒tgx=3⇒x=arctg3+⇒n,n∈z