If the equation kcosx−3sinx=k+1has a solution for x then
0≤k≤8
k≥4
2k≤1
k≤4
If kcosx-3sinx=k+1 has a solution, then -k2+9≤k+1≤k2+9 ⇒k+1≤k2+9 ⇒k+12≤k2+9 ⇒k≤4