Question

check answer @thesmartone @jim_thompson5910

Answer 1

\[\sin x = x - \dfrac{x^3}{3!} + \dfrac{x^5}{5!}-\dfrac{x^7}{7!}+\cdots \]

are you using that series ?

Answer 2

that works best when x is around 0

Answer 3

you could also cheat here by looking at options because only one option is positive

Answer 4

yes, i am.
thx @rational

Answer 5

yw