Cos(π/4-t)=cos(π/2-(π/4+t))=sin(π/4+t)
cos(5π/12+t)=cos(π/2-(π/12-t))=sin(π/12-t)
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cos(π/4+t)cos(π/12-t)-sin(π/4+t)sin(π/12-t)=cos(π/4+t+π/12-t)=
=cosπ/3=1/2
Уравнение: (x - (5-√12)/4)(x- (5+√12)/4)=0,
x^2 -x(5-√12)/4 -x(5+√12)/4 + (5-√12)(5+√12)/16=0,
x^2 -5x/4 +x√12/4 -5x/4 -x√12/4 +(25-12)/16=0,
x^2-10x/4+13/16=0,
16x^2-40x+13=0
1) 0,9
2) 20,5
3) 133,5
4) 0,1
5) 1
6) 10,5
1)(4х-4у)(4х+4у)
1)(2а-3в)(2а-3в)
дальше не помню извини