Is it possible to use align inside a array environment?

Question

I am preparing a class and I ran into this problem... Is it possible to use align inside a array environment?

I was thinking of putting 4 equations as the elements of a matrix. But the first element contains 2 rows, aligned as below

\begin{array}{ll}
\begin{align*}
d_1 &=\frac{ ln\left(\frac{F^P_{t,T}(S)}{F^P_{t,T}(K)}\right) + \left(\frac{ \sigma^2}{2}\right) (T-t)} {\sigma \sqrt{T-t}}\\
&= \frac{ ln\left(\frac{90.1242}{90.3668}\right) + \left(\frac{ 0.25^2}{2}\right) (1)} {0.25 \sqrt{1}}=0.1142
\end{align*}                                               &            N(d_1)=\\ 
d_2=0.1142 - 0.25 = -0.1358                               &         N(d_2)= \] 

Probably it is not possible because both use the symbol &. Any suggestions?

Thanks

Answer 1

amsmath provides many environments like aligned, alignedat etc which may be handy for such cases. For details, refer to amsldoc (texdoc amsldoc from terminal)

Here is a shot using aligned:

 \documentclass{article}
\usepackage{amsmath}
\begin{document}
  \[\begin{array}{ll}
\begin{aligned}%[t]
d_1 &=\frac{ \ln\left(\frac{F^P_{t,T}(S)}{F^P_{t,T}(K)}\right) + \left(\frac{ \sigma^2}{2}\right) (T-t)} {σ\sqrt{T-t}}\\
&= \frac{ \ln\left(\frac{90.1242}{90.3668}\right) + \left(\frac{ 0.25^2}{2}\right) (1)} {0.25 \sqrt{1}}=0.1142
\end{aligned}                                               &            N(d_1)=\\
d_2=0.1142 - 0.25 = -0.1358                               &         N(d_2)=
\end{array}
\]
\end{document}

If you want to align at more than one point, you may consider using alignedat.

A better way would be to use alignedat alone without array.

Answer 2

In my experience, the benefits of constructing complicated layouts often do not exceed their drawbacks. For instance, your students might completely overlook the N(d_1) and N(d_2) parts if they're stuck far to the right of the other material. Your students may be better off, I suspect, if the material is presented with a single vertical alignment axis, which may be constructed with an align* environment. To improve the intelligibility of the typeset material, I'd spend time getting consistent sizes of the large parentheses in each of the major parts of the math material.

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{align*}
d_1 
&=\frac{ \ln\Bigl(\frac{F^P_{t,T}(S)}{F^P_{t,T}(K)}\Bigr)  % use \Big[lr] instead of \left and \right
    + \left(\frac{ \sigma^2}{2}\right) (T-t)} {\sigma \sqrt{T-t}}\\
&= \frac{ \ln\left(\frac{90.1242}{90.3668}\right) 
    + \bigl(\frac{ 0.25^2}{2}\bigr) (1)} {0.25 \sqrt{1}}=0.1142\\ % use \big[lr] instead of \left and \right
N(d_1) &= \dots\\[2ex]  % provide a bit more vertical space
d_2 &=0.1142 - 0.25 = -0.1358\\
N(d_2) &= \dots\\
\end{align*}
\end{document}