<span>cos17cos73=0.5(cos90+cos56)</span>
<span><span>sin13cos21=0.5(sin34-sin8)</span></span>
<span><span><span>cos4cos86=0.5(cos90+cos82)</span></span></span>
<span><span><span>cos90=0</span></span></span>
<span><span><span>cos56=cos(90-34)=sin34</span></span></span>
<span><span><span>cos82=cos(90-8)=sin8</span></span></span>
<span><span><span><span>cos17cos73-sin13cos21-cos4cos86=0.5(sin34-sin34+sin8-sin8)=0</span></span></span></span>
X - y - 1 = 0
y = x - 1
см скрин
=================
<span>(10x^2+1/3a^2)^3
1000x^6+3*100x^4*1/3a^2+3*10x^2*1/9a^4+1/27a^6
1000x^6+100a^2x^4+3 1/3a^4x^2+1/27a^6
Решал способом : (a+b)^3 = a^3 + 3a^2b + 3ab^2 + b^3</span>