Y =14cosx+7√3x -7√3π/3 +6. ; x∈[ 0;π/2]
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max(y ) --?
y'(x) = -14sinx+7√3 = -14(sinx -√3/2).
y'(x)=0 ;
sinx=√3/2 *** x= (-1)^k +π*k ,k ∈Z ***
x =π/3 ∈[0;π/2]
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y(a) =y(0) =14cos0 +7√3*0 -7√3π/3+6 = 20 - 7√3π/3 ;
y(π/3) =14cosπ/3 +7√3*π/3 -7√3π/3+6 =13 ;
y(b) =y(π/2) =14cosπ/2 +7√3*π/2 - 7√3*π/3 +6= 7√3*π/2 - 7√3*π/3 +6
max(y ) = y(π/3) =13.