Common FormulasCIRCUMFERENCE Circle:
 C = πd, in which π is 3.1416 and d the diameter.
AREA Triangle:
 A = (ab)/2 , in which a is the base and b the height.
 Square:
 A = a^{2}, in which a is one of the sides.
 Rectangle:
 A = ab, in which a is the base and b the height.
 Trapezoid:
 A = (h(a + b))/2, in which h is the height, a the longer parallel side, and b the shorter.
 Regular pentagon:
 A = 1.720a^{2}, in which a is one of the sides.
 Regular hexagon:
 A = 2.598a^{2}, in which a is one of the sides.
 Regular octagon:
 A = 4.828a^{2}, in which a is one of the sides.
 Circle:
 A = πr^{2}, in which π is 3.1416 and r the radius.
VOLUME Cube:
 V = a^{3}, in which a is one of the edges.
 Rectangular prism:
 V = abc, in which a is the length, b is the width, and c the depth.
 Pyramid:
 V = (Ah)/3, in which A is the area of the base and h the height.
 Cylinder:
 V = πr^{2}h, in which π is 3.1416, r the radius of the base, and h the height.
 Cone:
 V = (πr^{2}h)/3, in which π is 3.1416, r theradius of the base, and h the height.
 Sphere:
 V = (4πr^{3})/3, in which π is 3.1416 and r the radius.
TEMPERATURE SCALES Degrees Fahrenheit to Degrees Celsius:
 T_{C} = ^{5}/9 (T_{F} – 32)
 Degrees Celsius to Degrees Fahrenheit:
 T_{F} = ^{9}/5 T_{C} + 32
 Degrees Celsius to Kelvins:
 T_{K} = T_{C} + 273.15
MISCELLANEOUS Distance in feet traveled by falling body:
 d = 16t^{2}, in which t is the time in seconds.
 Speed of sound in feet per second through any given temperature of air:
 take the square root of (273 + t), in which t is the temperature Centigrade, multiply it by 1087, and divide the result by 16.52.
 Cost in cents of operation of electrical device:
 C = (Wtc)/1000, in which W is the number of watts,t the time in hours, and c the cost in cents per kilowatthour.
 Conversion of matter into energy (Einstein's Theorem):
 E = mc^{2}, in which E is the energy in ergs, m the mass of the matter in grams, and c the speed of light in centimeters per second: (c^{2} = 9 × 10^{20})
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