X=3π/2+y
sin(3π/2+y)-cosy=-√2
-cosy-cosy=-√2
-2cosy=-√2
cosy=√2/2
y=+-arcos√2/2 +2πn, n∈Z
y=+-π/4+2πn
x=3π/2+y=+-π/4+3π/2+2πn
Трекгольник ABC
AB=13
BC=7
AC-?
AB^2=BC^2+AC^2
13^2=7^2+AC
AC^2=AB^2-BC^2
AC^2=169-49
AC=корень из 120
X(x-3)≤0
x=0 x=3
+ _ +
----------[0]------------------[3]---------------------
x∈[0;3]