3.8Theorems,
La
ws,
.
.
.
57
escapes
to
text
mo
de.
Use
\mathrm
insteadto
k
eep
the
size
switc
hing
mec
h-
anism
activ
e.
But
pa
y
atten
tion,
\mathrm
willonly
w
ork
w
ell
on
short
items.
Spaces
are
still
not
activ
e
and
accen
ted
c
haracters
do
not
w
ork.
5
\begin{equation}2^{\textrm{nd}}
\quad
2^{\mathrm{nd}}
\end{equation}
2
nd
2
nd
(3.10)
Sometimesy
ou
still
need
to
tell
L
A
TE
X
the
correct
fon
t
size.
In
math
mo
de,
this
is
set
with
the
follo
wing
four
commands:
\displaystyle
(123),
\textstyle
(123),
\scriptstyle
(
123
)and
\scriptscriptstyle
(
123
).Changing
st
yles
also
affects
the
w
a
y
limits
are
displa
y
ed.
\begin{displaymath}\mathop{\mathrm{corr}}(X,Y)=
\frac{\displaystyle
\sum_{i=1}^n(x_i-\overline
x)
(y_i-\overline
y)}
{\displaystyle\biggl[
\sum_{i=1}^n(x_i-\overline
x)^2
\sum_{i=1}^n(y_i-\overline
y)^2
\biggr]^{1/2}}
\end{displaymath}
corr(
X,
Y
)=
n
㑘
i
=1
(
x
i
−
x
)(
y
i
−
y
)
㐔
n
㑘
i
=1
(
x
i
−
x
)
2
n
㑘
i
=1
(
y
i
−
y
)
2
㐕
1
/
2
Thisis
an
examples
with
larger
brac
k
ets
than
\left[\right]
provides.
The
\biggl
and
\biggr
commandsare
used
for
left
and
righ
t
brac
k
ets
resp
ectiv
ely
.
3.8Theorems,
La
ws,
.
.
.
Whenwriting
mathematical
do
cumen
ts,
y
ou
probably
need
a
w
a
y
to
t
yp
eset
“Lemmas”,
“Definitions”,
“Axioms”
and
similar
structures.
L
A
TE
X
supp
orts
this
with
the
command
\newtheorem{
name
}[
counter
]{
text
}[
section
]
The
name
argument
is
a
short
k
eyw
ord
used
to
iden
tify
the
“theorem.”
With
the
text
argument
y
ou
define
the
actual
name
of
the
“theorem,”
whic
h
will
b
e
prin
ted
in
the
final
do
cumen
t.
5
The
AM
S
-L
A
TE
X
(
amsmath
)pac
k
age
mak
es
the
\textrm
commandw
ork
with
size
c
hanging.