
area of triangle
1/2 base x height

pythagorean theorem
only for right triangles
a^{2 }+ b^{2 }= c^{2}

right triangle ratios
(4)
 3:4:5
 5:12:13
 s : s : s/2
 s : s/3 : 2s

area of square
(2)
 s^{2}
 1/2 d^{2}^{ } d=diagonal

area of rhombus, 4 equal sides, 4 angles that aren't necessary right angles
1/2 d1 d2

area of parallelogram
2 opposite and equal pairs of sides
base x height

area of rapezoid
1/2 (b_{1} + b_{2}) x h

total interior angle
(n2) 180
n=number of sides

average measure of one angle in polygon
(n2)180 / n

volume of polygon
area of the base x height

volume of a cylinder
(pie r^{2}) height

total surface area of a cube
6e^{2}

total surface area of rectangular solid
2(l w) + 2 (w h) + 2 (h l)

total surface area of a cylinder
(circumference x height) + 2(pie r^{2})

distance between 2 points
/ (x_{2}  x_{1})^{2 }+ (y_{2}  y_{1})^{2}

circumference of circle
2pie r
pie d

area of circle
pie r^{2 }

length of an arc
 1. find the circumference of the circle (2pie r, pie d)
 2. put the degree measure* of the arc over 360, reduce fraction
 3. multiply circumference by the fraction

area of a sector
 1. find area of the circle (r^{2})
 2 . put degree measure* of sector over 360, reduce
 3. multiply the area by the fraction

equations for FOIL
 (a+b)^{2 } = a^{2} + 2ab + b^{2 }
 (ab)^{2 } = a^{2}  2ab + b^{2 }
 (ab)(a+b) = a^{2}  b^{2}^{ }

find probability
number of possible desired outcomes/ number of total possible outcomes

find distance
 distance = rate x time
 time = distance/ rate
 etc

average
sum/ number of terms

average common sense way
average is 90
numbers: 89, 88, 93, 92 90
1, 2, +3, +2
 = +2
 need to get 88 to get average (subtract the number extra or add number needed)

percent increase or decrease
number increase or decrease/ original whole

interest problems
 PRTI
 Principal x Rate x Time = Interest
 principal:amount money begin with
 rate: interest rate you're earning on the money, expressed as a decimal
 time: amt of time (years) money left in account
 interest: amt of interest earn on the investment

work
time put in/ capacity, time to do the whole job

