利用公式:{{1}^{2}}+{{2}^{2}}+{{3}^{2}}+\cdot \cdot \cdot +{{n}^{2}}=\frac{n(n+1)(2n+1)}{6},计算:{{2}^{2}}+{{4}^{2}}+{{6}^{2}}+\cdot \cdot \cdot +{{60}^{2}}= . 相关知识点: 试题来源: 解析 37820 提公因数:{{2}^{2}}+{{4}^...
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\partial {{a}_{j}}}+\sum\limits_{i,j,k=1}^{2}{\frac{\Delta {{x}_{i}}\Delta {{x}_{j}}\Delta {{x}_{k}}}{3!}\frac{{{\partial }^{3}}f\left( {\vec{a}} \right)}{\partial {{a}_{i}}\partial {{a}_{j}}\partial {{a}_{k}}}+\cdot \cdot \cdot }\] ...
因为Y1~Yn服从标准正态分布,而Zi为其线性组合,因此Zi也服从正态分布。 E(Zi)=E(ai1Y1+ai2Y2+ai3Y3+……+ainYn)=∑k=1naikE(Yk) 由于E(Yk)=0,所以:E(Zi)=0; D(Zi)=ai12D(Y1)+ai22D(Y2)+ai32D(Y3)+……+ain2D(Yn)=∑k=1naik2D(Y) 由(1)式得:D(Z_{i})=1\cdot D(Y)=1。
e Charge density difference and f spin density. Full size image We studied the electronic structure of the Fe-N4 site and O2 to understand the activation mechanism of *O2. Before the adsorption of O2, the projected density of state (PDOS) of the Fe site indicates that the Fe site has ...
(8) {\lim}_{x{\to}{\infty}}(\frac{1}{(n+1)^{3}}+\cdot \cdot \cdot +\frac{1}{(2n)^{3}}
4.若n为自然数,则$$ \sqrt { \frac { 1 \cdot 2 \cdot 3 + 2 \cdot 4 \cdot 6 + \cdots n \cdot 2 n \cdot 3 n } { 1 \cdot 5 \cdot 1 0 + 2 \cdot 1 0 \cdot 2 0 + \cdots + n \cdot 5 n \cdot 1 0 n } } $$ ___ 相关知识点: 试题来源: 解析 ...
Introduction The notion of a submanifoldNof a manifoldMis a fundamental concept in (differential) geometry, playing a crucial role in various branches of mathematics and physics. A metric, connection, etc., onMuniquely induces (see, e.g., [43]) a metric, connection, etc., onN. In the la...
Two-dimensional (2D) ferromagnets with high Curie temperature TC are desirable for spintronics applications. However, they are rarely obtained in experiments mainly due to the challenge of synthesizing high-quality 2D crystals, and their TC values are be
\, e_\psi \wedge \frac{1}{2} \left( {\mathrm{sin}}~\theta _1~ \mathrm{d}\theta _1 \wedge \mathrm{d}\phi _1-{ b_1}~{\mathrm{sin}}~\theta _2~ \mathrm{d}\theta _2 \wedge \mathrm{d}\phi _2\right) \nonumber \\&\quad -\frac{3g_s mn_f}{4\pi } { a_2}~\...