5A Trigonometry with right-angled triangles5B Problems involving right-angled triangles5C Three-dimensional trigonometry5D Trigonometric functions of a general angle5E Quadrant, sign, and related acute angle5F Given one trigonometric function, find another5G Trigonometric identities5H Trigonometric equations5I The sine rule and the area formula5J The cosine rule5K Problems involving general triangle