How to render a "Edit" form partial in the "Show" page of another model in Rails

I want to display an "Edit" form in the "Show" view of a parent object.

My model looks like this: A Trip has many Days which has many Activities. Trip accepts nested attributes for Days. Days accepts nested Attributes for Activities.

When I am in the "Show" view for a Trip, how do I render an "Edit" form partial for an "Activity"?

I know I need to somehow specify to the Edit Form partial which Activity ID that I want to edit but I'm not sure how to pass along that information from the "Show" view of a "Trip".

    <% @trip.days.each do |day| %>
    <div id="daydiv_<%= day.id %>">
      <b><%= day.summary %></b>
        <%= content_tag_for :ol, day do %>
          <% day.activities.each do |activity| %>
                <li id="activity_<%= activity.id %>"><%= link_to activity.address, edit_activity_path(activity) %></li>
          <% end %>
      <% end %>
    </div>
    <% end %>

<div id="activity_form">
  <%= render :partial => "/activities/form", :activity => @activity  %>
</div> 

my /activities/form partial looks like this:

<%= form_for(@activity) do |f| %>
  <div class="field">
    <%= f.label :title %><br />
    <%= f.text_field :title %>
  </div>

  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>