# Geometry 400 FORMULAS

## Terms

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Midpoint
C1+C2/2
Number of triangles in a polygon
n - 2
Sum of interior angles of a regular polygon
180(n - 2)
Measure of exterior andles of a regular polygon
360/n
Measure of interior angles of a regular polygon
s/n
Number of diagonals from any vertex in a regular polygon
n - 3
Total number of diagonals
n(n - 3)/2
Proportion
P.O.M. = P.O.E.

a/b = c/d
Measure of a median of a triangle
1/2 base
distance formula
the square root of
(x - x)2 + (y - y)2
sine (-)
opposite side / hypotenuse
cosine
tangent
measure of a central angle
= measure of intercepted arc
measure of an inscribed angle
= 1/2 measure of intercepted arc
measure of an interior angle
= 1/2 sum of two intercepted arcs
measure of an exterior angle
= 1/2 difference of intercepted arcs
when a tangent segment intersects a secant segment...
tangent segment2 = outside times the whole thing.
when two secant segments intersect outside the circle....
the outside times the whole thing = the outside times the whole thing.
lateral area of a prism
perimeter of base x height
lateral area of a cylinder
2(pi)rh
total area of a prism and cylinder
lateral area + 2 (base area)
volulme of a prism
base area x height
volume of a cylinder
(pi)r2h
lateral area of a pyramid
slant height (perimeter) / 2
lateral area of a cone
(pi)r x slant height
total area of a cone and pyramid
lateral area + base area
area of a sphere
4(pi)r2
volume of a sphere
4(pi)r3/3
# of faces
s + 2
# of verticies
2s
# edges
3s
perimeter of a polygon
sum of sides
circumference of a circle
(pi)d
length of an arc
m. of arc x circumference/360
area of a parallelogram
bh
area of a rhombus, square, kite
d x d/2
area of a triangle
bh/2
area of a triangle (w/ semiperimeter)
square root of
s(s-a)(s-b)(s-c)
area of an equilateral triangle
s2 / 4 (square root of 3)
area of a trapezoid
(b + b)h/2
area of a circle
(pi)r2
area of a regular polygon
ap/2
area of a sector
m. of arc x area of circle / 360
area of a segment
area of a sector - area of a triangle
area of a triangle (w. sine)
1/2ab sine c

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