The fifth-seeded Radwanska took an early 4-1 lead and won the first set in 33 minutes. The Polish player faltered in the second when Jankovic broke twice.
Radwanska regrouped and wrapped up the match without losing another game. She said she regained her confidence by breaking early in the third set.
“She just start to play much better in the second set. I was really in trouble,” Radwanska said. “But in the third set, I was just trying to be focused on my game and just fight until the end. I really get more confident after that, and I think she get a bit angry.”
Defending champion Caroline Wozniacki will play unseeded Julia Goerges of Germany in the second semifinal later Friday.
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