3 added 88 characters in body edited Apr 16 '14 at 0:27 bill s 56.4k33 gold badges8080 silver badges161161 bronze badges One straightforward way to take the conjugate of an expression is to replace I with -I ComplexExpand[I Cos[z] Sin[y] + Sin[z] + A (Cos[z] - I Sin[y] Sin[z])] //. I -> (-I) A Cos[z] + Sin[z] - I (Cos[z] Sin[y] - A Sin[y] Sin[z])  As Szabolcs points out in the comments, this solution can be problematic, so beware! One straightforward way to take the conjugate of an expression is to replace I with -I ComplexExpand[I Cos[z] Sin[y] + Sin[z] + A (Cos[z] - I Sin[y] Sin[z])] //. I -> (-I) A Cos[z] + Sin[z] - I (Cos[z] Sin[y] - A Sin[y] Sin[z])  One straightforward way to take the conjugate of an expression is to replace I with -I ComplexExpand[I Cos[z] Sin[y] + Sin[z] + A (Cos[z] - I Sin[y] Sin[z])] //. I -> (-I) A Cos[z] + Sin[z] - I (Cos[z] Sin[y] - A Sin[y] Sin[z])  As Szabolcs points out in the comments, this solution can be problematic, so beware! 2 deleted 31 characters in body edited Jul 10 '13 at 18:40 bill s 56.4k33 gold badges8080 silver badges161161 bronze badges I think Conjugate only works on numerical data. You canOne straightforward way to take the conjugate of thean expression by replacingis to replace I with -I ComplexExpand[I Cos[z] Sin[y] + Sin[z] + A (Cos[z] - I Sin[y] Sin[z])] //. I -> (-I) A Cos[z] + Sin[z] - I (Cos[z] Sin[y] - A Sin[y] Sin[z])  I think Conjugate only works on numerical data. You can take the conjugate of the expression by replacing I with -I ComplexExpand[I Cos[z] Sin[y] + Sin[z] + A (Cos[z] - I Sin[y] Sin[z])] //. I -> (-I) A Cos[z] + Sin[z] - I (Cos[z] Sin[y] - A Sin[y] Sin[z])  One straightforward way to take the conjugate of an expression is to replace I with -I ComplexExpand[I Cos[z] Sin[y] + Sin[z] + A (Cos[z] - I Sin[y] Sin[z])] //. I -> (-I) A Cos[z] + Sin[z] - I (Cos[z] Sin[y] - A Sin[y] Sin[z])  1 answered Jul 10 '13 at 18:15 bill s 56.4k33 gold badges8080 silver badges161161 bronze badges I think Conjugate only works on numerical data. You can take the conjugate of the expression by replacing I with -I ComplexExpand[I Cos[z] Sin[y] + Sin[z] + A (Cos[z] - I Sin[y] Sin[z])] //. I -> (-I) A Cos[z] + Sin[z] - I (Cos[z] Sin[y] - A Sin[y] Sin[z])