# If A, B and C be the angles of a triangle, then out of the following, the incorrect relation is:

- cot ((A+B)/2) =tan C/2
- cos ((A+B)/2)=sin (C/2)
- sin((A+B)/2) =cos (C/2)
- tan ((A+B)/2) = sec (C/2)

**Answer: (4) tan (A + B)/2 = sec C/2**

- cot ((A+B)/2) =tan C/2
- cos ((A+B)/2)=sin (C/2)
- sin((A+B)/2) =cos (C/2)
- tan ((A+B)/2) = sec (C/2)

**Answer: (4) tan (A + B)/2 = sec C/2**