If the function f(x)=Ksin x+2cos xsin x+cos xis strictly increasing for all values of x, then
K<1
K>1
K<2
K>2
Since f(x)=Ksin x+2cos xsin x+cos x is strictly increasing for all x,f′(x)>0 for all xor (K−2)sec2x(sinx+cosx)2>0 for all xor K−2>0 or K>2