[tex] \large\color{lime}\boxed{\colorbox{black}{Answer : - }}[/tex]
We know that, in ∆ABC,
∠A+∠B+∠C = 180°
But the triangle is right angled at C
ie., ∠C = 90°
Therefore, ∠A+∠B+ 90° = 180°
⇒ ∠A + ∠B = 90°
Therefore, cos(A + B) = cos 90º = 0
