Question

1 + cos (4x) + cos(8x) + cos(12x)....+ (cos nx).

Answer 1

There is a direct formula for this:

\[\large{\sum_{i = 0}^{n} \cos{(2ix)} = \csc{x}\sin{((n+1)x)}\cos{(nx)}}\]

Answer 2

In this question, you have to replace n by n/2.

Answer 3

@megprowder will this help you ?

Answer 4

thx

Answer 5

Np

Answer 6

@megprowder - If you think @vishweshshrimali5 helped you, then you can give him a medal. You can also fan him and write a testimonial in order to appreciate his work.

Also, welcome to OpenStudy! :)