The min. value of 2sinx+2cosx=
1
21−12
21/3
0
We have
2sinx+2cosx2≥2sinx·2cosx ∵AM≥GM ≥2sinx+cosx2 ≥2-22 ≥2-12 ⇒2sinx+2cosx≥2.2-12 ≥21-12