Core5 mapped NDA questions
Build the idea
Build exam-ready understanding by connecting the core idea, formulas or facts, worked example and previous NDA questions. Focus on why each rule works, then test it under timed conditions.
Concept
These apply trigonometry to triangles and to real-world distance problems. The sine and cosine rules relate sides and angles in any triangle; heights-and-distances problems use angles of elevation and depression.
Drawing a clear figure is half the solution.
Key Points & Formulas
- Sine rule: a/sinA = b/sinB = c/sinC = 2R.
- Cosine rule: c² = a² + b² − 2ab cosC.
- Area = ½ ab sinC = √[s(s−a)(s−b)(s−c)] (Heron), s = (a+b+c)/2.
- Angle of elevation/depression is measured from the horizontal.
Worked Example
Q. A tower subtends an angle of 30° at a point 60 m from its base on level ground. Find its height.
tan30° = height / 60.
height = 60 × tan30° = 60 × (1/√3) = 60/√3 = 20√3 ≈ 34.6 m.