Maths · Class 11 · Chapter 9
Straight Lines
10 lessons 84 min 2 simulations
This chapter describes a straight line with algebra. It starts from the distance, section and area formulas of earlier classes, defines the inclination and slope of a line, and uses slopes to test for parallel and perpendicular lines and to find the angle between two lines. It then writes the equation of a line in point-slope, two-point, slope-intercept and intercept form, meets the general equation Ax + By + C = 0, and ends with the distance of a point from a line and the distance between two parallel lines.
What the exam asks
For JEE Main, straight lines carry steady marks: slopes and the angle formula, the right form of equation for the data given, the perpendicular distance formula, the distance between parallel lines, concurrency, and the foot of the perpendicular or the image of a point in a line. JEE also asks about the normal form, families of lines through a point of intersection, angle bisectors and the position of a point relative to a line, which the rationalised text touches only lightly, so they need practice from other material.
Lessons
10 lessons · 84 min
1Coordinate geometry recapNCERT §9.17 min2Slope of a lineNCERT §9.26 min3Slope from two pointsNCERT §9.2.110 min 1 sim4Parallel and perpendicular linesNCERT §9.2.27 min5Angle between two linesNCERT §9.2.37 min6Point-slope and two-point formsNCERT §9.3.1, §9.3.2, §9.3.37 min7Slope-intercept and intercept formsNCERT §9.3.4, §9.3.57 min8Point-to-line distanceNCERT §9.411 min 1 sim9Distance between parallel linesNCERT §9.4.18 min10Chapter reviewMust-know facts, traps and formulas14 min