a^2+4a-7=(5-√2)^2+4*(5-√2)-7=
<span>7!=1*2*3*4*5*6*7=</span>5040
<span>sinxsiny=1/a cosxcosy=</span><span>1/b
сos(x-y)-cos(x+y)= </span><span>2/a
</span>сos(x-y)+cos(x+y)=2/b
2сos(x-y)=2/a+2/b cos(x-y)=(a+b )/ab x-y=+- arccos[(a+b )/ab]+2πk
2cos(x+y)=2/b-2/a cos(x+y)=(a-b )/ab x+y= +-arccos[(a-b )/ab]+2πm
x=+-0.5arccos[(a+b )/ab]+-0.5arccos[(a-b )/ab]+π(k+m)
y=+-0.5arccos[(a-b )/ab]+-0.5arccos[(a+b )/ab]+π(m-k) m,k∈Z