幾何 Formulas

$P = 4s,\quad A = s^2$

$P = 2l + 2w,\quad A = l \cdot w$

$A = \tfrac{1}{2} b h$

$A = \sqrt{s(s-a)(s-b)(s-c)},\ s=\tfrac{a+b+c}{2}$

$A = b h$

$A = \tfrac{1}{2}(b_1 + b_2) h$

$C = 2\pi r,\quad A = \pi r^2$

$A = \tfrac{1}{2} P a$

$V = s^3$

$V = l \cdot w \cdot h$

$V = \pi r^2 h$

$V = \tfrac{1}{3}\pi r^2 h$

$V = \tfrac{4}{3}\pi r^3$

$V = \tfrac{1}{3} s^2 h$

$SA = 6 s^2$

$SA = 2(lw + lh + wh)$

$SA = 2\pi r^2 + 2\pi r h$

$SA = 4\pi r^2$

$SA = \pi r^2 + \pi r \ell,\ \ell=\sqrt{r^2+h^2}$

$a^2 + b^2 = c^2$

$d = \sqrt{(x_2-x_1)^2 + (y_2-y_1)^2}$

$30°-60°-90°: 1 : \sqrt{3} : 2$

$45°-45°-90°: 1 : 1 : \sqrt{2}$

$A + B + C = 180°$

$S = (n - 2) \cdot 180°$

$\theta_{\text{inscribed}} = \tfrac{1}{2}\theta_{\text{central}}$

$s = r\theta$

$A = \tfrac{1}{2} r^2 \theta$

$M = \bigl(\tfrac{x_1+x_2}{2}, \tfrac{y_1+y_2}{2}\bigr)$

$m = \tfrac{y_2 - y_1}{x_2 - x_1}$

$(x-h)^2 + (y-k)^2 = r^2$