The correct option is B x=π6
f(x)=1+2sinx+2cos2x
⇒f'(x)=2cosx+2(2cosx)(−sinx)
⇒f'(x)=2cosx(1−sinx)
For max/min, f′(x)=0⇒cosx=0 or sinx=12
⇒x=π2,π6
Now,
⇒f''(x)=ddx(2cosx−2sin2x)=−2sinx−4cos2x
Clearly, f"(π6)=−3<0, and f′′(π2)=2>0
Hence maximum value of f will occur at x=π6