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Area of a triangle
1/2 (base)(height)

Special Right Traingles
 345 (or any multiple of); right triangle; given any 2find 3rd side length
 306090; side ratio of X:Xsqrt(3):2X
 51213 (or any multiple of); right triangle;given any 2find 3rd side length
 454590; side ratio of X:X:Xsqrt(2)

Circumference of a circle
2(pi)r

Arclength
If n is a degree measure
 S= 1(n/360)(2pi(r))
 S=(ratio of degree part:whole)(circumference)


Area of a circular sector
If n is the degree measue of the sector's central angle
 A= 1(n/360)(pi(r^2))
 A=(ratio of degree of sector:degree of circle)(area of circle)

Interior Angles of a polygon
The sum of the interior angles of a polygon= (n2)(180), where n is the number of sides

Surface area of a rectangular solid
2lw+2wh+2lh

Volume of a rectangular solid

Volume of a cylinder
(pi)(r^2)(h)

Percent formula
Part= (perecnt)(whole)

Probability
Favorable/Possible

Solving an inequality
When multiplying or dividing both sides by a negative number you must reverse the sign

Midpoint between
(x1, y1), (x2, y2)
= [(x1+x2)/2], [(y1+y2)/2]

Divisible by 2
If last digit is divisible by 2

Divisible by 3
If the SUM of its digits is divisible by 3

Divisible by 4
If last two digits are divisble by 4

Divisible by 5
Ends in 0 or 5

Divisible by 6
If it is divisible by both 2 (last two digists divisible by 2) and 3 (SUM of its digits is divisble by 3)

Divisible by 9
If the SUM of its digits is divisible by 9

First 25 primes (<100)
2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97

complimentary lines
make up a right angle

supplementary lines
make up a straight line

Ratio of areas of two similar triangles
square of the ratio of corresponding lengths
(if triangle b is twice the size of triangle a, (2/1)^2=4; 4 times the area of triangle a)

Special right traingle side length ratios
1:1:(sqrt)2 isosceles right triangles
1:(sqrt)3:2 306090 triangle

pythagorean triplets
3,4,5 (and any multiple of these e.g., 6,8,10)
5,12,13 (and any multiple of these)

Surface area of a cylinder
 A=(circumfrence of circular base)(height)+(2area of circular bases)
 A=[(2pi(r)h)] + [2(pi)r^2)]

The diagonal through a box
d^2=(l^2)+(w^2)+(h^2)

Area of a trapeziod
1/2(b1+b2)(h)

Counting Principle
two tsks; N ways to do/choices for the first and M was to do/choices for the second
 (NM)
 Use anytime a question asks, "how many" (ways to do..., numbers between..., arrangments of...)

Probability an experiment will replicate
 (probability of first event)(probability of second)(...)...
 [ex; coin landing heads 3x in a row; (1/2)(1/2)(1/2)=1/8]

Probability of E and F occurring
 Independent: p(E and F) = p(E) x p(F)
 Dependent: p(E and F) = p(E) x p(FlE)
 Conditional: p(FlE) = p(E and F)/p(E)
 0 if mutually exclusive

Probability of E or F occurring
 p(E)+p(F)  p(E and F)
 If mutually exclusive: p(E)+p(F)

Common factorials
 0!=1
 1!=1
 2!=2
 3!=6
 4!=24
 5!=120
 6!=5040

Permutation (without replacement) (nPr)
(ways to select officers)
 The number of ways of obtaining an ordered subset of elements from a set of elements is given by
 nPr=n!/(nr)!

Permutation (with replacement) (nPr)
"permutation lock"
n^r

Combination (without order) (nCr)
 Number of combinations of n distict objects taken r at a time
 n!/[r!(nr)!] = nPr/r!

