Concept:Use trigonometric identities to simplify the product before integrating.Explanation:Let I=∫sec2xcsc2xdx.Write sec2x=cos2x1 and csc2x=sin2x1.So I=∫sin2xcos2x1dx.Use 1=sin2x+cos2x.Thus I=∫sin2xcos2xsin2x+cos2xdx.Split the fraction:I=∫(cos2x1+sin2x1)dx.I=∫(sec2x+csc2x)dx.Since ∫sec2xdx=tanx and ∫csc2xdx=−cotx.Therefore I=tanx−cotx+C.Answer:tanx−cotx+C, which matches option A.