∫18⋅(2sintcost)2⋅(2cos2t)dt
=∫18⋅sin22t⋅(1+cos2t)dt
=∫116⋅2sin22t⋅(1+cos2t)dt
=∫116⋅(1−cos4t)⋅(1+cos2t)dt
=116∫(1−cos4t)⋅(1+cos2t)dt
=116[∫dt+∫cos2tdt−∫cos4tdt−12∫(2cos4tcos2tdt)]
=116[∫dt+∫cos2tdt−∫cos4tdt−12∫(cos6t+cos2t)dt]
=116[t+12sin2t−14sin4t−112sin6t−14sin2t+c]
=116[t+14sin2t−14sin4t−112sin6t+c]