Question 735099
If f(x)= cos(2x)-3sin(4x), find the exact value of f'(PIE/6)
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For[0,2π]
f(x)= cos(2x)-3sin(4x)
f(π/6)=cos(2π/6)-3sin(4π/6)
..
cos(2π/6)=cos(π/3)=1/2
sin(4π/6)=sin(2π/3)=√3/2 (in Q2 where sin>0)
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f(π/6)=cos(2π/6)-3sin(4π/6)
=cos(π/3)-3sin(2π/3)
=1/2-3√3/2
=(1-3√3)/2