answer for this question

As AB=BC, it implies that angle B is the right angle and equals 90 degrees.

Angle A = Angle C = 45 degrees.

Therefore, cos A + cos B = $\frac{1}{\sqrt{2}}$ + 0 =  $\frac{1}{\sqrt{2}}$

So the answer is option B.

The answer given is wrong and we have modified it. Thanks

1/root2+1/root2=root2