Chapter 2,
 Formulas
 A formula is a general representation of an equation (or relationship).
 A formula will have many variables and few specific numbers in it.
Example: v = d
t Evaluating Formulas
 Given: the formula.
 Given: values for all but one variable.
 Goal: determine the value of the unknown variable for the given variable values.
Example: evaluate v = d
tAnswer: v = 300 miles
5 hours= 60 mph.  Solving for One Variable of a Formula
 Given: the formula.
 Asked to: solve for a particular variable.
 Goal: isolate the particular variable on the left hand side with everything else on the right hand side.
Example: given v = d
tAnswer: t = d
v Subscripts
 Subscripts are smaller numbers or letters placed to the lower right of letters.
 Formulas often contain variables with subscripts.

 Examples
 x_{1} is read "x sub 1" and 1 is the subscript.
 R_{k} is read "R sub k" and k is the subscript.
 Some Greek Letters (and Common Meanings)
 Greek letters are often used in formulas.
 Some greek letters have meanings that are usually associated with them.
Letter Meaning (small pi) a constant (see to 1000 places) (small theta) an angle (capital sigma) summation of many (capital pi) product of many  Some Common Formulas
Formula Use A = r^{2} Area of a circle.
r is the radiusC = 2r Circumference of a circle.
r is the radiusA = LW Area of a rectangle.
L is length, W is widthP = 2L + 2W Perimeter of a rectangle.
L is length, W is widthA = 1
2BH Area of a triangle.
B is base length, H is heighta^{2} + b^{2} = c^{2} Pythagoean theorem for a right triangle.
a, b lengths of legs
c length of hypotenuseA = Prt Simple interest.
A is interest earned,
P is the principal,
r is the interest rate (decimal),
t is timeA = P(1 + r
n) ^{nt} Compound interest.
A is interest earned,
P is principal,
r is interest rate (decimal),
n is number of times interest is paid per year,
t is time in yearsA = Rt Rates.
A is amount, R is rate, t is timed = vt Distance and speed.
d is distance, v is speed, t is timeC = 5
9(F  32) Temperature conversion.
F is degrees Fahrenheit
C is degrees Centigrade