Evaluate : ∫sin(x+a)sin(x−a)dxAnswer: (x+a)cos2a−sin2alog∣sin(x+a)∣+CSolutionPut t=x+a, so dx=dt and x−a=t−2a. Expanding,sintsin(t−2a)=cos2a−sin2acott.Integrating,∫(cos2a−sin2acott)dt=tcos2a−sin2alog∣sint∣+C.Restoring t=x+a,(x+a)cos2a−sin2alog∣sin(x+a)∣+CCBSE Class 12 Board · 2013 · Subjective