Key TakeawaysPalantir Technologies jumped in premarket trading Monday following news that the big data analytics software company will join the benchmark S&P 500 index, with the inclusion taking effect before the market opens on Sept. 23.The stock temporarily broke down below an ascending triangle last month, but promptly reversed above the pattern's top trendline to form a bear trap.Investors should monitor key overhead chart levels in Palantir shares at $32.70 and$34.75, while eyeing important retracemen ...