// when the DOM is ready...
$(document).ready(function () {
  $("body.page-about section-about a.btn_getinvolved").click(function(){
    $("body.page-about .coda .selected").removeClass("selected");
    $("body.page-about #btn_coda_3").addClass("selected");
    
    $("body.page-about .coda_panel").hide();
    $("body.page-about #coda_3").show();
  });
});