$equation$
environment can be used to display and automatically number a single- line equationeqnarray
environment is used for displaying
and automatically numbering either a single expression that spreads
over several lines or multiple expressions, while taking care of
alignment for us. The syntax is similar to that of the
tabular
and array
environments, except that no argument
is necessary to declare the number and justification of columns. The
eqnarray*
environment does this without numbering any equations.
0.1
\begin{eqnarray} (a+b)(a+b) & = & a^2 + 2ab + b^2\\ (a+b)(a-b) & = & a^2 - b^2 \end{eqnarray}will give
(a + b)(a + b) | = | a2 +2ab + b2 | (1) |
(a + b)(a - b) | = | a2 - b2 | (2) |
See how we identify the columns so as to line the = signs up. We can also leave entries empty, to obtain effect like the following:
\begin{eqnarray*} \frac{d}{dx} \sin x & = & \lim_{h\rightarrow0}\frac{\sin(x+h)-\sin x}{h}\\ & = & \lim_{h\rightarrow0}\frac{\sin x\cos h + \cos x\sinh - \sin x}{h}\\ & = & \lim_{h\rightarrow0}\frac{\sin x(\cos h-1)}{h} + \cos x\frac{\sin h}{h}\\ & = & \cos x \end{eqnarray*}which produces
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= | cos x |