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Calculat.org

Area and perimeter

Online calculators calculate the area and circumference of plane geometric figures.
You can also find formulas, drawings and calculation procedures on the website.

Calculators

$$ \begin{aligned} A &= \pi r^2 \\ \\ C &= 2 \cdot \pi r \end{aligned} $$

$$ \begin{aligned} A &= \frac{a h_a}{2} \\ \\ P &= a + b + c \end{aligned} $$

right-angled triangle

$$ \begin{aligned} A &= \frac{ab}{2} \\ \\ P &= a + b + c \end{aligned} $$

$$ \begin{aligned} A &= a \cdot a = a^2 \\ \\ P &= 4 \cdot a \end{aligned} $$

$$ \begin{aligned} A &= ab \\ \\ P &= 2 \cdot (a + b) \end{aligned} $$

$$ \begin{aligned} A &= a h \\ \\ P &= 4 \cdot a \end{aligned} $$

$$ \begin{aligned} A &= a h_a = b h_b \\ \\ P &= 2 \cdot (a + b) \end{aligned} $$

$$ \begin{aligned} A &= \frac{(a + c)h}{2} \\ \\ P &= a + b + c + d \end{aligned} $$

regular pentagon

$$ \begin{aligned} A &= \frac{\sqrt{25 + 10 \sqrt{5}}}{4} a^2 \\ \\ P &= 5 \cdot a \end{aligned} $$

regular hexagon

$$ \begin{aligned} A &= \frac{3 \sqrt{3}}{2} a^2 \\ \\ P &= 6 \cdot a \end{aligned} $$

regular polygon

$$ \begin{aligned} A &= \frac{1}{4} n a^2 \cot\frac{180^\circ}{n} \\ \\ P &= n \cdot a \end{aligned} $$

Pythagorean theorem

$$ \begin{aligned} c^2 = a^2 + b^2 \end{aligned} $$

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