# How can I do this equation? [duplicate]

I'm new using latex, someone can help mw with this equation, please How can I do this equation?

## marked as duplicate by Au101, Stefan Pinnow, Andrew, Zarko, Werner equations StackExchange.ready(function() { if (StackExchange.options.isMobile) return; $('.dupe-hammer-message-hover:not(.hover-bound)').each(function() { var$hover = $(this).addClass('hover-bound'),$msg = $hover.siblings('.dupe-hammer-message');$hover.hover( function() { $hover.showInfoMessage('', { messageElement:$msg.clone().show(), transient: false, position: { my: 'bottom left', at: 'top center', offsetTop: -7 }, dismissable: false, relativeToBody: true }); }, function() { StackExchange.helpers.removeMessages(); } ); }); }); Oct 28 '16 at 21:31

• welcome to tex.sx. this question should be helpful: Math symbol question: Vertical bar for ''evaluated at …'' – barbara beeton Oct 28 '16 at 19:07
• Exactly as @barbarabeeton says. The fraction (assuming that's giving you difficulties) is $\frac{\delta T_{i}}{\delta D}$ (obviously the vertical line and the Q should also be within that same pair of $...$) – Au101 Oct 28 '16 at 19:09
• Thanks, the vertical bar was my problem. I didn't know the comand big. This is the code $\frac{\delta T_{i}}{\delta D} \big|_{q}$ – Christian Raine Oct 28 '16 at 19:22

$$\left. \frac{\delta T_i}{\delta D} \right|_Q$$