To find the limit of sin x + cos x for x--> pi/3, we first substitute x with pi/3 to see if we get a valid solution.
sin x + cos x for x--> pi/3
=> sin (pi/3) + cos (pi/3)
we see that both sin (pi/3) and cos (pi/3) are defined.
sin (pi/3) = (sqrt 3) /2
cos ( pi/3) = 1/2
sin (pi/3) + cos (pi/3) = (sqrt 3 + 1)/2
Therefore the required limit is (sqrt 3 + 1)/2