## gerryliyana 2 years ago Help

1. lillybeth123

huh?

2. abb0t

Is this a medical emergency? If so, please call your local emergency number.

3. gerryliyana

it's math emergency

4. lillybeth123

wats ur question?

5. gerryliyana

These are the pictures that I've uploaded for my question

6. lillybeth123

oh glob, sorry i cant help, thats too hard, bye. :)

7. abb0t

I vaguely remember doing this, but I think you want to use the exponential form of cosh and sinh to prove it.

8. cblrtopas

Yeah, noob google series expansion of hyperbolic cosine and sine

9. cblrtopas

So sin z is equal to some summation. You multiply it by i. Work out a few terms in the summation making sure to remember that i^2=-1 and try to simplify it to look like the sinh z formula.

10. gerryliyana

11. gerryliyana

For -1 < p < 1 prove that $\sum_{n=0 }^{\infty} p^{n}\cos nx =\frac{ 1= pcos x }{ 1-2pcosx + p^2 }$

12. cblrtopas

bleh too much effort