Question

My teacher gave me a question to expand cos4x in ascending powers of x including the x^4 term and I don't understand her solution, which is 1-8x^2 +(32/3)x^4. Can someone explain please?

Answer 1

Any particular method or formula or process that should be used?

Answer 2

urm, I'm not sure, most likely binomial theorem or something because that's the topic we're on

Answer 3

use the taylor series expansion for cosx

Answer 4

okay I'll try it! thanks so much! :)

Answer 5

I tried the Maclaurain's expansion, and it worked! thanks again :)

Answer 6

that'll work too

Answer 7

http://www.wolframalpha.com/input/?i=series+cos%284x%29+at+x%3D0

Answer 8

thanks @eliassaab !

Answer 9

YW