This was a labor of
html for me =) BTW 
formulas is also a valid plural form according to
MerriamWebster. Please message me if I made any errors which I'm sure I have.
Two Dimensional Objects
with side of
length a
Area =
a^{2}
Perimeter = 4
a
with sides of length
a and
width b:
Area =
ab
Perimeter = 2
a + 2
b
with
height h and
base b and side
a:
_________ ___
/ / 
/ / a h
/____b___/ __
th = acute angle between a and b
Area =
bh =
absin(
th)
Perimeter = 2
a + 2
b
with sides
a, b, c and height
h
___
/\ 
/ \ 
a/ \ c 
/ \ h
/ \ 
/____b_____\ __
Area = 0.5
bh = 0.5
ab sin(
th) =
sqrt(
s(
s
a)*(
s
b)*(
s
c))
s =
semiperimeter = 0.5 (
a +
b +
c)
Perimeter =
a +
b +
c
with sides
a and
b and height
h
______a______ ___
/ \ 
/ \ h
/ th ph\ 
/_________b_________\ __
Area = 0.5
h(
a+
b)
Perimeter =
a +
b +
h(
1/(sin(
th)) + 1/(sin(
ph))
with
n sides of length
b
Area = 0.25
nb^{2} cot(
pi/
n)
Perimeter =
nb
with
radius r
Area = pi
r^{2}
Perimeter (
Circumference) = 2 pi
r
with
semimajor axis a and
semiminor axis b
Area = pi
ab
Perimeter = 2 pi (0.5(
a^{2} +
b^{2})) ...approximately
more exactly, it is ...
0.5 pi
_
/

 / a^{2}b^{2} \^{0.5}
perimeter =   1  _____ sin(th)  dth
 \ a^{2 } /

_/
0
with height
a and width of base
b
Area = (2/3)
ab
Three Dimensional Objects
with side lengths
a, b, c
Volume =
abc
Surface Area = 2 (
ab +
bc +
ac)
tilted to angle
th
Volume =
abc sin(
th)
with radius
r
Volume = (4/3) pi
r^{3}
Surface Area = 4 pi
r^{2}
with radius
r and height
h
Volume = pi
r^{2}h
Lateral Surface Area = 2 pi
rh
Right Circular Cone
with height
h and radius of base
r
Volume = (1/3) pi
r^{2}h
Lateral Surface Area = pi
r(
r^{2} +
h^{2})
With base area =
A and height
h
Volume = (1/3)
Ah
with inner radius
a and outer radius
b
Volume = 0.25 pi
^{2} (
a +
b) (
b 
a)
^{2}
Surface Area = pi
^{2} (
b^{2} 
a^{2})
with semiaxes
a, b, c
Volume = (4/3)
abc
with height
a and base radius
b
Volume = 0.5 pi
b^{2}a
Analytic Geometry
the
distance d between two points in space  P
_{1}(a,b,c) and P
_{2}(x,y,z)
d = ( (xa)
^{2} + (yb)
^{2} + (zc)
^{2})
^{1/2}
P
_{1}(
x_{1},
y_{1}) and P
_{2}(
x_{2},
y_{2})
y_{2}  y_{1}
slope = _______
x_{2}  x_{1}