If △ABC is right angled at C, then the value of $\cos (A+B)$ is 

 

Given that, △ABC is right angled at C

$\Rightarrow 𝐴 + 𝐵 + 𝐶 = 180$

$\Rightarrow 𝐴 + 𝐵 = 180 - 𝐶$

$\Rightarrow 𝐴 + 𝐵 = 180 - 90$

$\Rightarrow 𝐴 + 𝐵 = 90$

$\Rightarrow 𝑐𝑜𝑠 (𝐴 + 𝐵) = 𝑐𝑜𝑠 90$

$\Rightarrow 𝑐𝑜𝑠 (𝐴 + 𝐵) = 0$

Hence option (𝑎)0 is correct