HETAV PATEL

Grade 11,

for what value of , the function f(x)=2cos2x-cos4x attains its absolute minimum in [0,pi]

for what value of , the function f(x)=2cos2x-cos4x

attains its absolute minimum in [0,pi]

Grade:12th pass

1 Answers

bharat bajaj IIT Delhi
askIITians Faculty 122 Points
10 years ago
f`(x) = -4sin 2x + 4sin4x = 0
sin 2x = sin 4x
sin 2x = 0 , or , cos 2x = 1/2
x = 0,90 or x = 30
f``(x) = -8cos2x + 16cos4x
Hence, absolute minimum is at x = 90 which is f(x) = -3
Thanks
Bharat Bajaj
askiitians faculty
IIT Delhi

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