6、P112例3.6(4),(5)7P142习题6(3),(4) X+2 arctan c 4x+82 2x+4-2 +4x+82x2+4x+8 +4+8 d(x+2) +4x+8(x+2)+2 X+2 In x+4x+ c 4三角有理式积分R( sinx,cosx知x 2t 令tan= t cOSX= dx=2dt 1+t2 1+t 2+sinx 2+ +t 1+t dt t+ arctan C 2 tan -+1 arctan +C3 6、P112例 3.6 (4),(5) 7 P142 习题 6 (3),(4) c 2 x 2 arctan 2 1 dx x 4x 8 1 2 + + = + +    + + + − = + + x 4x 8 2x 4 2 2 1 dx x 4x 8 1 2 2 ( ) ( ) d(x 2) x 2 2 1 x 4x 8 d x 4 8 2 1 2 2 2 2 + + + − + + + + =   c 2 x 2 arctan 2 1 ln x 4x 8 2 1 2 + + = + + − 4 0 三角有理式积分 ( ) R sinx, cosx dx 令 2 2 2 1 t 2t sinx 1 t 1 t t cosx 2 x tan + = + − = = 2 1 t 2dt dx + = 8、  + dx 2 sinx 1  +  + + = dt 1 t 2 1 t 2t 2 1 2 2  + + = dt t t 1 1 2        +          +      + = 2 1 d t 2 3 2 1 t 1 2 2 C 2 3 2 1 t arctan 3 2 + + = C 3 1 2 x 2tan arctan 3 2 + + =