Square

[[$ \qquad A =a^2 $]] ​
[[$ \qquad d = \sqrt {2}a $]]​

Rectangle

[[$ \qquad A =ab $]]​
[[$ \qquad d = \sqrt{a^2+b^2} $]]​

Rhombus

[[$ \qquad A =ah $]]​

Parallelogram

[[$ \qquad A = ah = ab \space \text{sin} \space \alpha $]]​

Trapezium

​[[$ \qquad A = \dfrac{1}{2}(a+b)h = \dfrac{1}{2}(a+b)s \space \text{sin} \space \alpha $]]​

Triangle

[[$ \qquad A= \dfrac{1}{2}ah = \dfrac{1}{2}ab \text{ sin } \alpha $]]​

Circle

[[$ \qquad A = \pi r^2 = \dfrac{1}{4} \pi d^2 $]]
[[$ \qquad p = 2 \pi r = \pi d $]]

Sector

[[$ \qquad b = \dfrac{\alpha}{360°} 2\pi r $]] (length of arc)
[[$ \qquad A = \dfrac{\alpha}{360°} \pi r^2 = \dfrac{br}{2} $]]​
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