I want to understand something very basic. How does trading work between BTC & USD.
Let's say I have 1 BTC at US 100. The naive idea is "buy low" and "sell high". But I don't grasp how that work, ie, how is possible to profit in both directions.
If the value of BTC change this way (value in USD):
110 85 102 40 70 90 115 130 100 200
What I need to do to turn a profit? And if my plan is that I don't lose more than I invest at the start?