## Important area formulas of 2D shapes

Polygon | Area |
---|---|

Rectangle | l × b |

Square | a × a = a^{2} |

Parallelogram | b × h |

Rhombus |
b × h
or $\frac{1}{2}\times {\mathrm{d}}_{1}\times {\mathrm{d}}_{2}$ |

Trapezium | $\frac{1}{2}\left(\mathrm{a\; +\; b}\right)\times h$ |

Triangle | $\frac{1}{2}\times b\times h$ |

Isosceles triangle | $\frac{b\sqrt{{a}^{2}\u2013{b}^{2}}}{4}$ |

Equilateral triangle | $\frac{\sqrt{3}}{4}{\mathrm{a}}^{2}$ |

Circle | πr^{2} |

## Important perimeter formulas of 2D shapes

Polygon | Perimeter |
---|---|

Rectangle | 2(l + b) |

Square | 4a |

Parallelogram | 2(a + b) |

Rhombus |
4a
or $2\sqrt{{{d}_{1}}^{2}+{{d}_{2}}^{2}}$ |

Trapezium | a + b + c + d |

Triangle | a + b + c |

Isosceles triangle | 2a + b |

Equilateral triangle | 3a |

Circle | Circumference = 2πr |