*Expanding list
 If a and b have the same sign, then a*b >= 0
 In general, A – B ≤  A – B 
  A – B  ≤  A  –  B . This is called the triangle inequality.
   A  –  B   ≤  A – B . This is an extension of the triangle inequality.
 The quotient a / b will end up being a terminating decimal number only if b can be written as the product of 2’s and 5’s when broken down into its prime factors. Stated another way, if you can write b = 2^{x}5^{y}, x ≥ 0, y ≥ 0, then the quotient a / b will be a terminating decimal value when it is calculated (e.g. 3 / 8 = 3 / 2^{3} = 0.375)
 Two lines the Cartesian plane are perpendicular if m_{1}m_{2} = 1

The angle between 2 lines on the cartesian plane is given by:
tan( a ) =  (m_{2} – m_{1}) / (1 + m_{1}m_{2}) 
Notice that if the lines are perpendicular, then the RHS becomes infinity.
 The sum of angles in any polygon is (V2)*180, where V is the number of vertices in the shape. See (V2) triangles to make any shape
 If you’re not sure how to solve a complex problem, try using the principle of superposition ;)

Interesting, but not very useful fact when it comes to programming with math:
max( a, b ) = 1/2( a + b +  a – b  )min( a, b ) = 1/2( a + b –  a – b  )
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