Pi

E

I

Pi // N

E // N

N[E]

I^2

1/0

0/0

N[Pi, 30]

Pi // Floor

Pi // Ceiling

Pi // Round

Prod[(i + 1)  x^i, {i, 0, 4}]

Product[(1 + i) (x^i), {i, 0, 4}]

Sum[(1 + i) (x^i), {i, 0, 4}]

(x + 2)^4 // Expand

(Cos[x] + Sin[x])^2

Expand[%]

% /. Cos[a_]^2 + Sin[a_]^2 -> 1

?? Function

#1^3&[x + 2]

cube[x_] := x^3

cube[2]

cube[-2]

cube[x + y]

cube[x + y] // Expand

g[x_, p_, q_] := (x - p)^2  +  q

g[2, 0, 0]

g[2, 1, 1]

Clear[cube]; Clear[g];

z = 3;

f[x_] := x^2  +  z

f[y]

f[x_] := Module[{z}, x^2 + z]

f[y]

f[x_] := Module[{z = 1}, x^2 + z]

f[y]

z

g[x_] := Block[{z}, x^2 + z]

g[y]

g[x_] := Block[{z = 1}, x^2 + z]

g[y]

z

intcube[n_Integer] := n*n*n

intcube[4]

intcube[1.2]

intpower[a_?Positive, n_Integer] := a^n

intpower[3, 4]

intpower[-2, 3]

intpower[a, 3]

2 < 5

2 < t

2 == 3

100 == 10^2

s1[x_] := -1 /; x < 0

s1[x_] := 0 /; x == 0

s1[x_] := 1 /; x > 0

s1[-10.1]

s1[0.0002]

s1[0]

s1[19^4]

ipower[m_Integer?Positive, 0] := 1

ipower[m_Integer?Positive, n_Integer?Positive] := 
      m*ipower[m, n - 1]

ipower[2, 5]

Needs["Miscellaneous`Units`"]

Convert[1  Meter, Feet]

Convert[1  Feet, Meter]

Needs["Miscellaneous`Calendar`"]

DayOfWeek[{1999, 12, 31}]