# Useful Formulae

4 TWODIMENSIONALFIGURES areas and perimeters Formul for the perimeters and areas of various twodimensional forms are given below. Circle Radius r, diameter d 2r Perimeter,or circumference 2r d Area r2 where 3.1415926... Ellipse Area ab a andb are the minor and major semiaxes respectively. The two illustrated points are its foci, such that l mis constant. Rectangle Area ab Perimeter 2a 2b Parallelogram Area bh ab sin Perimeter 2a 2b Trapezium Area h a b Perimeter a b h csc csc Regular ngon Area nb2cot180n Perimeter nb Sides and internal angles are all equal. Quadrilaterali Area ab sin Quadrilateralii Area h1 h2b ah1 ch2 5