sin 54- sin 18 = 2 sin (54-18 /2) *cos (54+18)/2=2 *sin18*cos72=2 sin^2(18)=1-cos36=
X·2+(x+5·2)=38
2x+x=38-10
3x=28
x=28÷3=9,33( длинна)
x-5=9,33-5=4,33(ширина)
=3с(а²-с²)=3с(а-с)(а+с)
=3а²с(8а-1)
=(10а-1)(10а+1)
=а(а²-b²)(a²+b²)
=(2-у)²
=3(у-4)²
=(2х+6)²
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