NDA Maths · Teaching notes
Straight Lines — NDA Mathematics
Lines (coordinate geometry of the straight line) is around 97 past-year NDA questions — a steady, high-volume scorer. The whole chapter is built from a handful of tools: the slope and the forms of a line's equation, the distance and section formulas, the angle between two lines, and the area of a triangle from its vertices. Work the four notes in order — first equations, slopes and the family of lines; then distance, section and locus; then angles, parallelism and perpendicularity; and finally triangles, quadrilaterals and polygons, which apply everything. The recurring traps are sign errors in the angle formula and forgetting that 'distance from a point to a line' needs the normalised form.
Subtopic notes
Equations, Slope & Family of Lines
27 PYQsThe slope of a line and the standard forms of its equation, the intercept form, the family of lines through a point or an intersection, and reflections in a line.
Open note
Distance, Section & Locus
22 PYQsDistances between points, from a point to a line, and between parallel lines; the section formula for dividing a segment; and locus equations from a geometric condition.
Open note
Angle Between Lines, Parallel & Perpendicular
16 PYQsThe angle between two lines from their slopes, and the slope conditions for lines to be parallel or perpendicular.
Open note
Triangles, Quadrilaterals & Polygons
32 PYQsCoordinate geometry applied to figures: the area of a triangle from its vertices, the triangle centres (centroid, incentre, circumcentre), constructing vertices from medians/altitudes, and quadrilateral relations.
Open note
PYQ weightage by concept
13 concepts · 97 PYQs — where the marks actually sit, so you know what to drill first
PYQ weightage by concept
13 concepts · 97 PYQs — where the marks actually sit, so you know what to drill first
| Concept | PYQs | Share |
|---|---|---|
| Slope and the forms of a line | 9 | 9% |
| Family of lines and concurrency | 9 | 9% |
| Intercept form and intercepts | 6 | 6% |
| Image of a point and reflections | 3 | 3% |
| Concept | PYQs | Share |
|---|---|---|
| Section formula and ratios | 9 | 9% |
| Distance: point-point, point-line, parallel lines | 8 | 8% |
| Locus from a condition | 5 | 5% |
| Concept | PYQs | Share |
|---|---|---|
| Angle between two lines | 12 | 12% |
| Parallel and perpendicular conditions | 4 | 4% |
| Concept | PYQs | Share |
|---|---|---|
| Parallelograms, squares and diagonals | 13 | 13% |
| Constructing a triangle: vertices, medians, altitudes | 11 | 11% |
| Area of a triangle and collinearity | 5 | 5% |
| Centroid, incentre, circumcentre | 3 | 3% |