Question

The period of cos(x+ 2x+3x+...+2x)is
1) 4r/n(n+1)
2) Ar/(1+1)
3) 47/n(n-1)
4) 42/(1-1)​

Answer 1

$\huge\bold\red{1) 4r/n(n+1)}$

Let f(x)=cos(x+2x+....+nx)

=cos( 2n(n+1) x).....( using ∑ r=0n r= 2n(n+1) )

=cos(x 2(n(n+1)))

period of cosx=2π

∴ periodof f(x)= n(n+1)2π×2 .................(as if period

of f(x)=p,period of f(mx)=p/m)

Answer 2

Step-by-step explanation:

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