math formulas

• what is the formula for the area of a trapezium?

  1/2 * (a+b) * h
• area of a circle?

  pi * r^2
• for a sector of angle x...


  arc length = (x/360) * 2 * pi * r

  area = (x/360) * pi * r^2
• surface area of hollow cylinder is...

  2 * pi * r * h
• surface area of hollow can is....

  (2 * pi * r * h) + pi * r^2
• surface area of a hollow cone is...

  pi * r * l
• surface area of a sphere is...

  4 pi * r^2
• volume of a solid with uniform cross section is...

  area of end * height
• volume of a sphere

  (4/3)*pi*r^3
• Rotational symmetry of order 2 means that if you rate the shape about its center through one complete turn, it will fit onto itself twice.
• Sum of interior angles in an N- sided polygon is?

  (n-2)*180
• in a regular n sided polygon, where all sides are qual and angles are the same, exterior angle is?

  360/n
• in a regular n sided polygon, where all sides are qual and angles are the same, interior angle is?

  180-(360/n)
• in quadratic sequence, the coefficient of n2 is always half the term by term rule in 2nd diff