8. H 為△ABC 的垂心，cos B＝、cos C＝。若於 E，且於 F。求 =？

14. A geometric transformation T：(x, y) → (x′, y′) consists of three transformations in order：● A rotation ofθ radians (0 ≤θ＜ 2π) about the origin, followed by● An enlargement with scale factor 2, centred at the origin, followed by● A translation of 1 unit right and 3 units down.Given that the transformation T maps the point to itself, find the angle θof the rotation.