Help with C2 question?

The question: A pendulum is set swinging. It's first oscillation is through 30 degrees. Each succeeding oscillation is 9/10 of the one before it. What is the total angle described by the pendulum before it stops?

bit stuck, how do I approach this question?

Thanks,

...

Each successive angle swung is smaller than the last by a factor of 9/10, and they get smaller over time but never reach 0. The first angle is 30 degrees. You have to add them all up, to infinity.

Is that enough of a hint?

Write out expression of total angle which conforms to an identifiable pattern.

Hope this helps.