Question

sinA+cosA=a then sinA-cosA=?

Answer 1

sinA=a-cosA.... eq (1)
cosA=a-sina... eq (2)
sinA-cosA=0
a-cosA-cosA=0.....(1,se)
-2cosA=-a
cosA=a/2
again..put in eq (2)
a/2=a-sinA
-sinA=a/2-a
sinA=a/2
from question
sinA-cosA=a/2-a/2=0
is your answer

Answer 2

Answer is 2-a
Hope you find the right answer or this is terribly wrong