1-cosA+cosB-cos(A+B)/1+cosA-cosB-cos(A+B)=tan(A/2)ct(A/2)

To simplify the given expression, we can make use of the half-angle identities for tangent and cotangent, as well as the trigonometric identity for cosines of the sum of angles. Here's how you can solve it step-by-step:

1. Start with the expression: (1 - cos(A) + cos(B) - cos(A+B)) / (1 + cos(A) - cos(B) - cos(A+B))

2. Apply the half-angle identities for tangent and cotangent:
tangent(A/2) = 1 - cos(A) / sin(A), and
cotangent(A/2) = 1 + cos(A) / sin(A)

3. We can rewrite the numerator and the denominator using these identities:
Numerator: (1 - cos(A)) + cos(B) - cos(A+B) = (1 - cos(A)) + cos(B) - (cos(A)cos(B) - sin(A)sin(B))

Denominator: (1 + cos(A)) - cos(B) - (cos(A)cos(B) - sin(A)sin(B))

4. Simplify the numerator:
(1 - cos(A)) + cos(B) - (cos(A)cos(B) - sin(A)sin(B))
= 1 - cos(A) + cos(B) - cos(A)cos(B) + sin(A)sin(B)

5. Simplify the denominator:
(1 + cos(A)) - cos(B) - (cos(A)cos(B) - sin(A)sin(B))
= 1 + cos(A) - cos(B) - cos(A)cos(B) + sin(A)sin(B)

6. Now, substitute the simplified numerator and denominator into the original expression:
(1 - cos(A) + cos(B) - cos(A)cos(B) + sin(A)sin(B)) / (1 + cos(A) - cos(B) - cos(A)cos(B) + sin(A)sin(B))

7. Notice that the terms involving sin(A)sin(B) cancel out in both the numerator and denominator:
= (1 - cos(A) + cos(B)) / (1 + cos(A) - cos(B))

8. Next, we can apply the trigonometric identity for cosines of the sum of angles:
cos(A+B) = cos(A)cos(B) - sin(A)sin(B)

9. Substitute the identity into the numerator:
= (1 - cos(A) + cos(B)) / (1 + cos(A) - cos(B) + cos(A+B))

10. The numerator and denominator both have 1 - cos(A) + cos(B) terms, so we can cancel them out:
= 1 / (1 + cos(A) - cos(B) + cos(A+B))

11. Finally, substitute the identity back into the denominator:
= 1 / (1 + cos(A) - cos(B) + cos(A)cos(B) - sin(A)sin(B))

12. This expression is equal to tangent(A/2) * cotangent(A/2):
= tan(A/2) * cot(A/2)

Therefore, we have simplified the given expression to tan(A/2) * cot(A/2).