Concept: The minimum and maximum value of asinx+bcosx −√a2+b2≤asinx+bcosx≤√a2+b2 Calculation: As we know, −√a2+b2≤asinx+bcosx≤√a2+b2 ⇒−√22+02≤2sinx+0cosx≤√22+02 ⇒−2≤2sinx≤2 ⇒−2≤2k+1≤2 ⇒−3≤2k≤1 ⇒−1.5≤k≤0.5 k=0,−1 Hence, Option 3 is correct.