True or false for sums and series?

Question

I know it is false but I don’t know what example I can use? I cannot use exponential series as an example because it’s not included in class work.

Answer 1

sinx = x - x³/3! + x⁵/5! - ... for all x

For any real number, x, the sum of the series is sinx, but the series is neither telescoping nor geometric.

For instance, sin(π/2) = (π/2) - (π/2)³/ 3! + (π/2)⁵ / 5! - ... = 1

Answer 2

The series could be arithmetic.