...........................................................
ctg(2(П/4+x))=ctg(П/2+2x)=tg2x cosx=sqrt(1-15^2/17^2)=-8/17
sin2x=2*8/17*15/17=240/289
cos2x=64/289-225/289=-161/289
tg2x=240/161 [П;5/4П]
tg2x=-240/161 [5/4П/3П/2]
Sin(3x+3π)=-sin2x
sin(3x+3π/2)=-cos3x
(-sin2x)*(-cos3x)-sin3x*cos2x=-1
sin2x*cos3x-sin3x*cos2x=-1
sin(2x-3x)=-1
sin(-x)=-1, -sinx=-1
sinx=1 частный случай
<u>x=π/2+2πn, n∈Z</u>
1 - 1/coskv a= (coskv a -1)/coskv a = - (1-coskv a)/coskv a = -(sinkv a)/coskv a = - tgkv a