Class XI Mathematics
Chapter 9: Straight Lines
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Syllabus Sections
Key Formulas & Equations
Click Copy to duplicateSlope Intercept Form
y = mx + c
Equation of line with slope m and y-intercept c.
Distance from Point to Line
d = \frac{|Ax_0 + By_0 + C|}{\sqrt{A^2 + B^2}}
Perpendicular distance from point (x0, y0) to line Ax + By + C = 0.
Perpendicular Slopes relation
m_1 m_2 = -1
Product of slopes of two perpendicular lines is -1.
Related Formulas from Adjacent Chapters
Sum of GP
S_n = \frac{a(r^n - 1)}{r - 1}
[From Sequences and Series] Sum of first n terms of a GP with common ratio r.
Sum of Infinite GP
S_\infty = \frac{a}{1 - r}
[From Sequences and Series] Sum of infinite terms of convergent GP (|r| < 1).