[Trigonometry for Games – Sprite Kit and Swift Tutorial: Part 1/2](http://www.raywenderlich.com/90520/trigonometry-games-sprite-kit-swift-tutorial-part-1) [Trigonometry for Games – Sprite Kit and Swift Tutorial: Part 2/2](http://www.raywenderlich.com/90521/trigonometry-games-sprite-kit-swift-tutorial-part-2)
