S=3,14*36=113,04
S=3,14*144=452,16
S=3,14*12,25=38,465
27.4-0.2y=1.6:0.08
27.4-0.2y=20
0.2y=27.4-20
0.2y=7.4
y=7.4:0.2
y=37
Преобразуем заданное в условии равенство:
Подставим найденное значение в выражение суммы:
Ответ: 100
<span>Угол между плоскостями </span>
7x - 4y - 4z + 5<span> = 0 и </span>
6x - 4y + z + 15 = 0
Косинус угла между плоскостями определяется по формуле:
<span><span><span>cos α = </span><span>|A</span></span></span>₁<span><span><span>·A</span></span></span>₂<span><span><span> + B</span></span></span>₁<span><span><span>·B</span></span></span>₂<span><span><span> + C</span></span></span>₁<span><span><span>·C</span></span></span>₂<span><span><span>| /</span></span><span>√(A</span></span>₁² + B₁² + C₁²)<span> √(A</span>₂² + B₂² + C₂²)
<span><span><span>cos α = </span>|7·6 + (-4)·(-4) + (-4)·1| /</span><span>√(<span>7</span></span></span>²<span><span><span> + (-4)</span></span></span>²<span><span><span> + (-4)</span></span></span>²)*<span><span>√(<span>6</span></span></span>²<span><span><span> + (-4)</span></span></span>²<span><span><span> + 1</span></span></span>²) <span><span>=
|42 + 16 + (-4)| / </span><span><span>√(49 + 16 + 16)* √(36 + 16 + 1) = 54 /(</span><span>√81*√53) =</span></span></span>
<span>= 54<span> / </span></span>√4293 <span><span>= <span><span>6√53 / </span>53</span> ≈ 0,824163.</span></span>