Геометрия

$S = \pi r^2$

$C = 2\pi r$

$S=a\cdot b$

$V=a\cdot b\cdot c$

$S_{\text{пов}}=2(ab+bc+ac)$

$\alpha + \beta = 180^\circ$

$\alpha = \beta$

$\alpha + \beta + \gamma = 180^\circ$

$\alpha_{\text{внеш}} = \beta + \gamma$

$P = a + b + c$

$P = 2(a + b)$

$S = ab$

$a\parallel b\Rightarrow \alpha=\beta,\quad \gamma+\delta=180^\circ$

$\alpha=\beta\Rightarrow a\parallel b,\quad \gamma+\delta=180^\circ\Rightarrow a\parallel b$

$a+b>c,\quad a+c>b,\quad b+c>a$

$\alpha+\beta=90^\circ$

$P=2a+b$

$\frac{\alpha}{2}+\frac{180^\circ-\alpha}{2}=90^\circ$

$AB=A_1B_1,\ AC=A_1C_1,\ \angle A=\angle A_1\Rightarrow \triangle ABC\cong\triangle A_1B_1C_1$

$AB=A_1B_1,\ \angle A=\angle A_1,\ \angle B=\angle B_1\Rightarrow \triangle ABC\cong\triangle A_1B_1C_1$

$AB=A_1B_1,\ BC=B_1C_1,\ AC=A_1C_1\Rightarrow \triangle ABC\cong\triangle A_1B_1C_1$

$\beta=\frac{\alpha}{2}$

$\beta=180^\circ-2\alpha$

$\alpha=60^\circ$

$P=3a$

$\gamma=180^\circ-\alpha-\beta$

$\alpha=\frac{180^\circ-\beta}{2}$

$\alpha+\beta=180^\circ$

$P=a_1+a_2+\dots+a_n$

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

$M\left(\frac{x_1+x_2}{2};\frac{y_1+y_2}{2}\right)$

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

$S = \frac{1}{2}ah$

$S = ah$

$S = \frac{a + b}{2}h$

$S = \frac{d_1d_2}{2}$

$m = \frac{a}{2}$

$S=\frac{1}{2}ah$

$M=\frac{l_{\text{чертеж}}}{l_{\text{натура}}}$

$S=\frac{a+b}{2}\cdot h$

$S=\frac{d_1d_2}{2}$

$m=\frac{a}{2}$

$\frac{AB}{BC}=\frac{A_1B_1}{B_1C_1}$

$\angle A=\angle A_1,\;\angle B=\angle B_1\Rightarrow \triangle ABC\sim\triangle A_1B_1C_1$