Common Formulas
Circumference
Circle:
C = 
d,
in which is
3.1416 and d the diameter.
Area
Triangle:
A = (ab)/2 , in which a is
the base and b the height.
Square:
A = a2, 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 = 1.720a2, in which a
is one of the sides.
Regular
hexagon:
A = 2.598a2, in which a
is one of the sides.
Regular
octagon:
A = 4.828a2, in which a
is one of the sides.
Circle:
A = 
r2,
in which is
3.1416 and r the radius.
Volume
Cube:
V = a3, 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 = r2h,
in which is
3.1416, r the radius of the base, and h the height.
Cone:
V = (r2h)/3,
in which is
3.1416, r theradius of the base, and h the height.
Sphere:
V = (4r3)/3,
in which is
3.1416 and r the radius.
Temperature Scales
Degrees
Fahrenheit to Degrees Celsius:
TC = 5/9 (TF
– 32)
Degrees
Celsius to Degrees Fahrenheit:
TF = 9/5 TC
+ 32
Degrees
Celsius to Kelvin:
TK = TC +
273.15
Miscellaneous
Distance in
feet traveled by falling body:
d = 16t2, 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 kilowatt-hour.
Conversion
of matter into energy (Einstein's Theorem):
E = mc2, 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: (c2 = 9 × 1020)