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raman malik Grade: 12
        

 the number of real values of x where the function f(x) = cosx+cos{(√2)x} attains its maximum is


(a) 0


(b) 1


(c) 2


(d) infinite

7 years ago

Answers : (1)

Badiuddin askIITians.ismu Expert
147 Points
										

Dear raman malik.


f(x) = cosx+cos{(√2)x}


f'(x)=-sin x -√2 sin √2x =0


    it gives x= 2m ∏/(√2 +1 )   and  (2m +1 ) ∏  /(√2 -1)  where m is any natural number


  clearly both values are not multiple of 2∏


only for m=0 


and f(0) = 1+1 =2 is its maximum value


so only one solution option b is correct


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Badiuddin


 


  

7 years ago
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