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(pi = = 3.141592...) Area FormulasNote: "ab" means "a" multiplied by "b". "a^{2}" means "a squared", which is the same as "a" times "a".Be careful!! Units count. Use the same units for all measurements. Examplessquare = a^{ 2} rectangle = ab parallelogram = bh trapezoid = h/2 (b_{1} + b_{2}) circle = pi r^{ 2} ellipse = pi r_{1} r_{2}
triangle given SAS (two sides and the opposite angle) triangle given a,b,c = [s(sa)(sb)(sc)] when s = (a+b+c)/2 (Heron's formula) regular polygon = (1/2) n sin(360°/n) S^{2} Area is measured in "square" units. The area of a figure is the number of squares required to cover it completely, like tiles on a floor. Area of a square = side times side. Since each side of a square is the same, it can simply be the length of one side squared. If a square has one side of 4 inches, the area would be 4 inches times 4 inches, or 16 square inches. (Square inches can also be written in^{2}.) Be sure to use the same units for all measurements. You cannot multiply feet times inches, it doesn't make a square measurement. The area of a rectangle is the length on the side times the width. If the width is 4 inches and the length is 6 feet, what is the area? NOT CORRECT .... 4 times 6 = 24 CORRECT.... 4 inches is the same as 1/3 feet. Area is 1/3 feet times 6 feet = 2 square feet. (or 2 sq. ft., or 2 ft^{2}). 


