Writing subscript in Mathjax?

Question

I want to type this .

I have tried like this

$$\lambda=\frac{0.693}{t_\frac{1}{2}}$$

Also,

$$\lambda=\frac{0.693}{{t}_\frac{1}{2}}$$

Also,

$$\lambda=\frac{0.693}{t_{\frac{1}{2}}}$$

But it don't work it display something like this

This code

also gives something that we don't want

Mathjax Configuration

<div class="layout"><script type="text/x-mathjax-config">
MathJax.Hub.Config({
  TeX: {extensions: ["AMSmath.js","AMSsymbols.js","mhchem.js","noErrors.js","noUndefined.js"]},
  tex2jax: {
      inlineMath: [ ['$','$'], ["\\(","\\)"] ],
      displayMath: [ ['$$','$$'], ["\\[","\\]"] ],
      processEscapes: true
    },
});
</script>
<script src="http://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS_HTML"></script>

Browser= Google Chrome OS= Windows 8.1

Answer 1

Use _{}

_{YOUR EXPRESSION}

Example:

$$Y_n = Y_{n-1}+{{(d/n)}sin(θ\pm n*Δ)}.$$  

Result: