K = \frac{1}{2}kA^2 \sin ^2 \left( {\omega t + \delta } \right)

% MathType!MTEF!2!1!+-
% feaafaart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn
% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqr1ngB
% PrgifHhDYfgasaacH8YjY-vipgYlh9vqqj-hEeeu0xXdbba9frFj0-
% OqFfea0dXdd9vqai-hGuQ8kuc9pgc9q8qqaq-dir-f0-yqaiVgFr0x
% fr-xfr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4sai
% abg2da9maalaaabaGaaGymaaqaaiaaikdaaaGaam4Aaiaadgeadaah
% aaWcbeqaaiaaikdaaaGcciGGZbGaaiyAaiaac6gadaahaaWcbeqaai
% aaikdaaaGcdaqadaqaaiabeM8a3jaadshacqGHRaWkcqaH0oazaiaa
% wIcacaGLPaaaaaa!483C!

Pasting the above "text" into MathType 5.0 will enter the above equation and make it possible to edit, save, and use in applications such as MS Word.