Limit

Sn=cos1+cos2+cos3+cos4+....+cosn

Find \lim_{n\rightarrow \infty}\frac{S_{n}}{n}

20 Answers

21
tapanmast Vora ·

Pl. reply Priyam/akand

33
Abhishek Priyam ·

[3]

21
tapanmast Vora ·

OH!!!

he he.....

i thot the first pink Akand got was for Q1....

NIce GOOGLY huh!!! [9]

33
Abhishek Priyam ·

and ya Q1 mein zero isliye aaya na kyunki Sum of n Roots of unity = 0 (for n>1

Q.1

21
tapanmast Vora ·

are upar me .. sin () cos() hai usko infinity se divide karnege to zero hi naa aega...

[7] wat? kis post ki baat kar raheho priyam

33
Abhishek Priyam ·

are upar me .. sin () cos() hai usko infinity se divide karnege to zero hi naa aega...

21
tapanmast Vora ·

Yah true.....

I gave the ans for n+1 terms.... with a lil calc mist. LOL.....

and ya Q1 mein zero isliye aaya na kyunki Sum of n Roots of unity = 0 (for n>1)

33
Abhishek Priyam ·

zero... for first... in book it was none of these :P

33
Abhishek Priyam ·

thoda alag hai...

cos(A+((n-1)B/2))sin(nB/2)
sin(B/2)

21
tapanmast Vora ·

ek aur dbt.

Q1 mein dont v hav ne specific answer?

33
Abhishek Priyam ·

cosA+cos(A+B)+cos(A+2B)+....+cos(A+(n-1)B)=?

21
tapanmast Vora ·

DUDEsss : is da ans to 2nd part = \cos ((2A + nB)/2)*\sin ((n+2)B/2)/sin(B/2)

1
Philip Calvert ·

yes bhaiya i understand........ (sorry who ek or thread .....
wo patanahi main kuch or soch raha tha.)

1
Akand ·

yup...i learnt it from nishant bhaiyya long back.......hehe

62
Lokesh Verma ·

Philip this is a standard trick... try to see that you understand it :)

It just kills some of the dirty tough looking summations. :)

1
Akand ·

y philip is it wrong???

1
Akand ·

NEXT WALA........

Z=real(Σei(A+rB))...r=0 to n-1......

1
Akand ·

so....Sn=real(ei/1-ei)
so the limit becomes...
I=real(ei/1-ei)/n
=(cos1-cos21-sin21)/n(1+cos21+2cos1+sin21)
= (cos1-1)/n(2+2cos1)
..........then i dont kno........ wel thanks to PRIYAM...
I forgot 1/∞=0...hehehehehe

33
Abhishek Priyam ·

Cool :)

1
Akand ·

eiθ=cosθ+isinθ
so......
ei+e2i...eni=cos1+cos2+...cosn+i(sin1+sin2...sinn)
real(Σeir)=Sn

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