First slide
Monotonicity
Question

If the function f(x)=Ksin x+2cos xsin x+cos xis strictly increasing for all values of x, then
 

Easy
Solution

Since f(x)=Ksin x+2cos xsin x+cos x is strictly increasing for all x,
f(x)>0 for all x
or (K2)sec2x(sinx+cosx)2>0 for all x
or K2>0 or K>2

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