Question

Prove that cos (-45°) + sin (-45°) = 0

Answer 1

cos(-45)= cos(45) = 1/root2      (1)

sin(-45)=-sin(45)=-1/root2          (2)
 

therefore from 1 AND 2 we get 
1/root 2 - 1/root2= 0

LHS=RHS