l> Area Formulas
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= 3.141592…) Area Formulas Note: “ab” means “a” multiplied by “b”. “a2” means “a squared”, which is the same as “a” times “a”. Be careful!! Units count. Use the same units for all measurements. Examples square = a 2 rectangle = ab parallelogram = bh trapezoid = h/2 (b1 + b2) circle = pi r 2 ellipse = pi r1 r2
|triangle =||one half times the base length times the height of the triangle|
|equilateral triangle =|
triangle given SAS (two sides and the opposite angle) = (1/2) a b sin C triangle given a,b,c =
when s = (a+b+c)/2 (Heron”s formula) regular polygon = (1/2) n sin(360°/n) S2 when n = # of sides and S = length from center to a corner
Units 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 in2.) Be sure to use the same units for all measurements.
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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 ft2).