三角形
求三角形面积
已知底和高
S=1/2×底×高 \frac{分子}{分母}
$$ \sum_{i=1}^{n} i = \frac{n(n+1)}{2} $$
\begin{align}
f(x) &= ax^2 + bx + c \\
f'(x) &= 2ax + b \\
f''(x) &= 2a
\end{align}$$
\begin{aligned}
a & =b+c \\
& =d+e
\end{aligned}
$$
S=1/2×底×高 \frac{分子}{分母}
$$ \sum_{i=1}^{n} i = \frac{n(n+1)}{2} $$
\begin{align}
f(x) &= ax^2 + bx + c \\
f'(x) &= 2ax + b \\
f''(x) &= 2a
\end{align}$$
\begin{aligned}
a & =b+c \\
& =d+e
\end{aligned}
$$