:confused:giup em bai nay voi em xin cam on :confused::confused: \int_{}^{} dx(cotg 3x)^11/(cos3x)^21 \int_{}^{}dx (tan 6x)^20/ (cos6x)^8 \int_{}^{} dx(tanx)^4/(cosx)^4 \int_{}^{}dx(cot2x)^6/(cos2x^5